It looks like this is actually related to https://www.drupal.org/project/zendesk/issues/3348376 🐛 Invalid iat parameter Fixed and is an issue with Dynamic Page Cache.
Looks like uncommenting this line:
$settings['cache']['bins']['dynamic_page_cache'] = 'cache.backend.null';
Fixes the issue
It's definitely a caching issue - Zendesk confirmed through their logs that a request iat value was the same 6 minutes later which is beyond their 3 minute tolerance.
Unfortunately, debugging this is beyond my knowledge.
However, what I have done to confirm it is the cache is enable the Mix module and put the site into Development mode and this fully resolves the issue which means its the either the Twig cache, backend cache or browser/proxy cache as these are disabled by the Mix module in dev mode.
For anyone else with this issue - the solution is in the notes but isn't clear. This affects Interactive Book and can be resolved by going to admin/config/system/h5p and setting "Enable LRS dependent content types"
Strangely, clearing the cache under Performance on Drupal does allow the user to login briefly to Zendesk via SSO.
If it helps - two further things I've done to rule things out:
Tried changing the following in the ZendeskSSOController.php file:
Changed $url variable to static domain with /access/jwt - no change
Changed getRequestTime() to getCurrentTime() - no change
Thanks for the reply. This is an example of what was sent - apparently it should be standard integer with no decimals so I'm assuming Unix Timestamp
nathanjon123 → created an issue.
nathanjon123 → created an issue.
More context - caches cleared, running latest version and no errors are shown on site or in logs.
h5p_points table in database is empty