Consider me a detective on the case of those pop-up errors. This thread has been primarily discussing matters within QuickBooks Online, which doesn't need to be updated on the user's end. Most errors in the program can usually be resolved by clearing your browser's cache.
Web-based platforms like QBO collect these files (cookies) to save you time when loading repetitive data and images. These files can often become outdated or corrupted, causing errors like the one you've mentioned. Clearing them out usually resolves such errors, and the links below will help you accomplish that in all supported browsers:
Clearing Temporary Cache Files
Doing this will force QBO to load a fresh copy of everything on the screen. Please know I'm always available should you ever need a helping hand with QuickBooks. Thanks for coming to the Community and have a wonderful rest of your day.