Welcome to the Community. Let's isolate this case by opening QuickBooks using an incognito or private browser. This helps us identify if it's related to a browser issue. Too much-stored data file may lead to unusual behaviors in QuickBooks.
Here's how:
Google Chrome: Press CTRL + Shift + N.
Internet Explorer: Press CTRL + Shift + P.
Safari: Press Command + Shift + N.
Mozilla Firefox: Press CTRL + Shift + P.
If it works, go back to your main browser and clear its cache to remove the browser's history. I also recommend using other supported browsers. This can be a temporary issue with the browser that you're using when opening QBO.