Customer not appearing in Azure Lighthouse after deploying ARM template in their environment

Question

I'm setting up Azure Lighthouse for our MSSP to access client instances of Sentinel. I have imported Lighthouse ARM template into client environment and can confirm the Service Provider page shows my MSSP tenant correctly, and delegations are appearing.
However, in my company Azure tenant, nothing appears on the Azure Lighthouse page, and their subscription doesn't appear in the subscription filter page. I have confirmed Group ID's are correct, and we have all the correct roles - even added Contributor to the group permissions to rule this out. I have tried delegating both subscriptions and just resource groups, but can't get anything to work (even left it for over a week incase it was taking ages to kick into gear)
Weirdly enough, we have a second Azure tenant with an entirely different tenant ID and associated domain linked (from before I started); when I use this tenant as the service provider ID (and update group IDs in the offer etc), delegation works perfectly and can access the client Sentinel instance without any issues.
Any thoughts on some advanced level of setting that might prevent Azure Lighthouse to work?
Only major difference I can see is that my main tenant doesn't have an actual Azure subscription - we are just using the free $100 credit from the action pack (but has a credit card attached for overages), whilst the second tenant that I got Lighthouse working in has a proper paid Azure plan that has been in place for 12 months.

Answer 1

Maybe a config issue with the offer template. I recommend using the creation wizard on the Lighthouse page. Try creating a new template. There should be an option in the portal to open a support request if all else fails.