TB 16.0.1 IMAP mail not saved locally problem

please advise

tried out TB's IMAP to access gmail account, but have a big problem

no matter that Sync options are set to download mail to local folder, and no restrictions of date or size are in place, i still can not force thunderbird to store mail locally (ie, work offline).

if there is no internet connection, than on some computers TB still shows all gmail folders, and mail headers, but no text is there.

or the same usb flash on other computer without internet, just wont show any mail folders at all.

as i said sync options are turned on (dowload mail locally, do not delete, and no options for date and size are used)

please help me out,
ty

edit:
regular - non portable version of TB does not have this problem.
mail viewed via IMAP is available offline in the same imap folder. mail setup is exactly the same in both versions