Hello,
I do use Power Automate with different tenants and for a while, it was working fine.
Until I've tried to purchase the premium subscription of Flow from my main tenant.
Now, I cannot access my second tenant. If I try to use the URLs to access to the second tenant, I receive a 404 error.
Also, tenants are not listed in the environments option, there's always one (the one I'm connected). But it doesn't give me the option to change from one tenant to another.
Do you know how can I fix that? And, do I need a premium license for each tenant?
Do you see the missing environments in powerplatform admin center ? If not somehow you lose the access rights to them. Ask a general admin to check your rights on each environment.