Update 1.5.1 to 1.6: Unable to start session

After a manual update from 1.5.1 to 1.6 I got 'Unable to start session.'
What to do?

I have the same problem as described in another thread: 301 Moved Permanently

Problem solved: make tmp/sessions writetable…

works! thanks!

Thanks for the report. Created a bug to show a better error message in the next release: Error "unable to start session" instead of a proper error message · Issue #2717 · matomo-org/matomo · GitHub