Activity list is not showing in contacts after upgrade to latest civicrm 5.9.1
I would suggest that you try clearing the cache first of all to see if that helps.  You can do this by deleting the files in the templates_c folder.  The location of this will depend on your CMS.  You can find more details in the documentation on upgrades.

If that doesn't help please edit you question to provide some more detail (including which CMS you are using).