can you clarify since you are mentioning Win 10 and Win 11, are you using "Desktop" (menu across the top) or "Online" (in your browser, menu down the left)? If you upgraded to Win 11 why not stick with desktop version?
for the import issues a lot of people have been having problems with browser permissions this year, see this thread and others
https://ttlc.intuit.com/community/taxes/discussion/re-vanguard-brokerage-update-is-available-from-va...
not sure about your transfer issue. folks have issue with transfer on desktop when starting a new return have solved it by doing File / Open Tax Return then opening the .tax2024 file and TT 2025 will detect prior year and transfer it into a new return.
if you're still having issues maybe post more details and screenshots using the camera icon above the message window (don't post any personal identifiers) and maybe someone here can help.
