Why did owncloud stop syncing after updating?

Question

Data synchronization

It costs owncloud 2.1.0
Windows 7 64bit
After installing the new version of owncloud, a red cross in the tray constantly appears, in owncloud itself it says that access is denied, what should
I do?
already on two computers, where the client was updated

Answer 1

What version of ownCloud is on the server?
Perhaps the 2.1 client requires a newer version of the server?
I have version 8.2.1-8.2.2 on the server, they work fine. Versions 8.1.x should also work.

Answer 2

I have a server on a virtual machine from bitnami, judging by its name, version 8.1.1 How can
I update the ownCloud server on a virtual machine?