Glad you got it sorted! So it was not Win10 at all, this time...
Yep, nor was it an AV issue, neither Windows Security (which includes Windows Defender AV & Windows Firewall) or 3rd party WebRoot SecureAnywhere AV.
The issue was also shown to not be related to any outbound data traffic (which also would indicate my box as a suspect...but I did see a lot of outbound data activity that was happening at the same time & only in conjunction w\ the AHIII outbound data traffic over TCP port 80 tying up this port which to me looked suspicious) but was verified related to inbound data traffic issues only that were happening before it reached my box BUT was isolated in tandem to only 1 source.....AHIII game servers which Hitech knew were using the std Web HTTP Service protocols over TCP Port 80 to download game data over the Internet directly to their game client software on my box, which is very weird since other software's online servers which use the very same std Web HTTP Service protocols over the very same port were having no issues getting incoming data into my box blocked by the OS itself (this part is a real legit function of Win 10 which was verified when I tried to run a separate piece of MS software that did conflict w\ the OS's 64 bit function & got the same error dialog as I got when patching up AHIII client to latest version....which the AV firewalls aren't written to detect) so my CenturyLink ADSL modem\router was somehow altering the direct AHIII server incoming data packet's header info\data packets themselves in a way that the Win 10 OS (not the AV firewalls) saw it as faulty & thus rejected it but if the same data packets came thru another source like MS Edge Web browser then my CenturyLink ADSL modem\router passed it thru untouched so then the OS saw it as clean so allowed it to be processed then the game would function as normal afterwards.
All diagnostics tests ran & all service logs looked at from the CenturyLink CT1100 (made by Actiontec) ADSL 1-Gbit modem\router came back as normal\clean operations so no hint of any pending issue within the unit itself & the unit was using the latest firmware so there was no path to doing a refresh to see if it straightened up & all other components downstream of it all passed my testing so there was nothing to suggest it was a suspect until we tested my box thru another path to the Internet which then the results of this test exposed my modem\router as a suspect.
Hitech offered to get w\ my CenturyLink ISP provider to run some tests between their AHIII servers & CenturyLink's DSLAM here in Farmington (gave him my account #) to see if my issue was occurring somewhere within CenturyLink's system before it got to my residence (was waiting on feedback from him before I did anything as I was gonna have to order another CenturyLink-compatible replacement ADSL modem\router....all stores in my area have stopped selling these since FIOS was installed some 5 yrs ago....online pickings are very thin at best). Hadn't heard from him yet but I got to thinking bout my old Netgear Nighthawk AC1900 ADSL WiFi 1-Gbit modem\router (CenturyLink approved) that had issues shortly after a firmware update (why I replaced it) so I got it out, hooked it back up then after a LOT of fiddling I finally got my IPhone to run the Netgear Genie setup software in it on Safari after performing multiple resets to default settings to get it signed back into CenturyLink's ISP then I could use the wife's computer (IE 11...MS Edge had issues displaying the Netgear Genie HTML graphics imaging even w\ IE11 compatibility enabled....) thru Ethernet to access it to then flash it to the latest firmware which was successful so then fixed it.
After setting all back up I then ran the game & tested it using the Steal the Sheep arena (uses only 1 terrain file) by deleting the stealshe.res terrain file from the ah3terr folder then clicking online to enter this arena (AHIII servers check the FE's ah3terr folder to see if the terrain file is present-if not then they will download the necessary terrain file to the FE to use in the arena, does the same process for all online arenas)....AHIII servers successfully downloaded the terrain files into the FE thru this Netgear Nighthawk ADSL modem\router w\o Win 10 OS interference & opened the arena so the issue was now no more...just as it had done thru the Verizon hotspot thru USB.
Hell of a deal w\ a lot of rabbit chasing on my part but we got it isolated to the source.....still don't know what exactly is the specific cause of this issue within this CenturyLink modem\router....a simple firmware upgrade may very well fix it but as of today CenturyLink hasn't posted any & I didn't see any on Actiontec's web site for this model either.
But as usual, when you do this kind of diagnosis work, you end up finding more unrelated issues....the WAP I was using to extend wireless Internet service to the rear of the house had gotten cut out since I installed my new CPU\mobo upgrade (mobo NIC is full 1-Gbit capable as is my Netgear switch but my old Zoom WAP thru it's WLAN port is not which caused severe WAP wireless data traffic slowdowns between it & the full 1-Gbit capable ADSL modem\router since the single Ethernet port was set for full 1-Gbit speeds between it, the switch & my box's NIC) so now I've ordered a TP-Link WAP\1-Gbit Ethernet router to replace the old Zoom unit to rectify this issue so the entire LAN system now will have the same 2.4G\5G wireless WAP LAN capability AND the same 1-Gbit Ethernet LAN speeds so I can take full advantage of the 5G wireless LAN speeds w\ the devices that can use it as well as full 1-Gbit Ethernet LAN speeds across all Ethernet connected devices.
Should be all hunky dory after this for a while...........I hope.