Invalid login request: The selected iss is invalid:
The LMS is sending an "iss" (issuer) of the request, that is not the same as the one registered on H5P.com.
This can typically be if your LMS is hosted in a special way, or on a separate subdomain.
In this case, we have to compare the data that is sent from the LMS with the configuration of the LTI connection on H5P.com.
One way to figure out what the LMS is sending is to generate a .HAR (HTTP Archive) file, which can be used to check for the data. This can be generated by following the instructions at https://aws.amazon.com/premiumsupport/knowledge-center/support-case-browser-har-file/and applying this method when entering the page that is showing the error.
This .HAR file can then be sent to support to be analyzed.