When using Multiple IDPs receive the error "Unable to Validate Signature"

[jonberardi]

Unable to authenticate when adding multiple IDPs, receive "Unable to Validate Signature" when authenticating.

Details:

• Can successfully authenticate with a single IDP
• When adding multiple IDPs (by adding four metadata URLS in the config) I can see that four IDPs have been added, and are active
• When authenticating with multiple IDPs, only a single IDP works at one time

Background:
I have a single Moodle instance with four subdomains: e.g. sub1.moodle.com, sub2.moodle.com
Azure has four separate applications created for each subdomain
The goal is for each individual subdomain to be accessible. Currently only one can be accessed at a time