2 Answers

This may be analyzing the domain name, which will take about 3-10 minutes to complete. The result is as follows:
end1.png
Sometimes it may take a day to complete the analysis, encryption, etc.

If your custom domain is still in a "Pending" state, it may take longer than expected; in my case, it took around 4 hours.

Also, if you're using Cloudflare, make sure to:

Set the CNAME record correctly to the target provided by your platform.

Disable the proxy (orange cloud) and set it to DNS only (grey cloud) during the verification process.
The proxy can block or delay domain verification.