I see many people have been having the same issue and i'm wondering if I might be able to get some help as well here. I've been getting pretty non-stop Disconnects that have been plaguing me since Heavensward practically, Its caused me to cancel my sub several times now but I really do like the game so I kept coming back.

I believe its the 90001 error which i believe is just a general disconnect error so that may not be helpful but basically, i'll drop out of existence, no lag or anything and hop right back in no "Character still logged in" message or anything like that either, but i never lose internet.

Things I've tried to fix it:
I opened the suggested ports on my gateway settings
Adjusted the settings in Internet Explorer to ensure the proper permissions were there.
Clean start up, No background programs
Hardwired connection and Wireless connection
Adjusted my firewall

I currently am running on my laptop and these happen randomly throughout the day, I may have an hour where it doesn't happen but then i'll get like a solid 4-5 hours of every 5 or so minutes of it.