Subdomain with underscores on github pages

I wasn’t able to enable https for my project site - https://github.com/ayrat555/el%5Fmonitorro (el_monitorro.badykov.com/)

it was returning the following error:

Certificate Request Error: Certificate provisioning will retry automatically in a short period, please be patient.

It turns out GitHub can’t generate an ssl ceriticate for subdomains with underscores.

When I changed the subdomain to elmonitorro, the ssl certificate was finally generated

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