If your users receive this message,
" Your account has not yet been connected to Salesforce. Please contact your admin to set up the connection "
It means that they are trying to login using the "Login with Salesforce" with their credentials and for some reason, they are not included in the master Salesforce user report that syncs to Hoopla.
Check out the criteria you have set for your Salesforce user report by going to the Salesforce Integrations area and scroll down to the User Provisioning area. Then click on "See report in Salesforce"