I have this exact issue and have done all these suggested fixes to no avail. It is just crazy that this post string began in 2019 and Quickbooks still has not fixed it!  Also just weird they have it marked as solved - what?? C'mon you guys, create a patch or something that allows us all to click on the alert and delete it - every time I sign on now I just roll my eyes that it is still sitting there from over a month ago, and now see I may have this stupid alert for as long as I use QBO. UGH!