I had some issues with windows 10 these helped me, also do it 1 step then test because all steps may not be needed.
1. Disable AV(some still run disabled so get a better AV :P i use kasperskyis)
2. right click select properties
3. press comaptibility tab check Run as administrator
4. check run in compatibility mode select windows 7
5. go into the gw2 folder and rename gw2.exe to Gw2.exe(didnt work? change Gw2.exe to gw2.exe sometimes unf in windows 10 loves to love and hate that "G/g")
6. right click gw2.exe press properties go to compatibility check the run as administrator box(no need for compatibility mode windows7)
7. hopefully fixed.
bonus fixes for alot of programs not working with windows 10
8. make sure the Visual C++ 2012(2010-15) Redistributable x86 and x64 packages are installed also Direct X is installed with all the .net packages (windows 10 doesn't always come with .net 3.0,3.5 they might need installed for some programs)