Hi there, @denis.
 
I have tracked your post and you mentioned a resolution to use another browser aside from Firefox. I suggest contacting our Chat Support Team so that they can view the issue and raise an investigation.
 
Also, you can check this article to know more details about the system requirements for QBO: System requirements for QuickBooks Online, QuickBooks Online Accountant, and QuickBooks Self-Employe....
 
Let me know if you have other concerns. I’d be glad to help you out. Take care.