Hi Taha,
Please check status of the solution is Deployed or not? If not please find out the errors why it is not successfully deployed on to Prod tenant.
On the test tenant whether this custom solution is in scope of the implementation project or not, please check? if not in scope please once again create a patch in test, scope the same and deploy it once again to prod tenant. After deploying you should be able to see the custom developed work centre floor plan in the list of work centres under Application User Management, where you should be able to assign it to the users.
Please try this out.
Regards
Hanu