Example: I own domain1.com
I made orangedoor.com an add-on domain with the host.

In AHREF's on an internal page on orange.codoorm/article1, it is showing one page backlinking to it.

orangedoor.domain1 dot.com/deep-page

So what is going on here or what do I need to fix?

I have had a canonical tag for years on the header.

Thanks