Last year, Firefox got stricter about third party cookies. If your bank uses multiple different servers -- you would notice the server changing in the address bar as you move between functions on their site -- Firefox may no longer be sharing your cookies among the sites. To try to work around this, turn off Enhanced Tracking Protection on the various bank sites. These include their main site, their login page, and potentially a third server used for online banking functions. To do that, simply click the shield icon at the left end of the address bar (next to the lock) and then click the slider switch at the top of the drop-down panel.
Any improvement?
As for what YouTube is up to, hmm, that is a strange message. Do you use any add-ons for blocking video ads or recording videos? Maybe one of those has suddenly become incompatible with YouTube (or may I should say, YouTube might not want them to work any more).
More generally, you could consider posting on the Mozilla Support site. They have a team of support volunteers to troubleshoot malfunctions with your currently installed version of Firefox, while this site is focused on idea submissions for future versions of Firefox (looking ahead anywhere from 8 weeks to many months). Here's a link to the new question form (for Windows/Mac/Linux): https://mzl.la/3y1vQUQ
