GitLab Pages Custom Domain SSL cert import issue

I failed to import signed SSL certificate by Positive SSL/Sectigo.

I got the signed certificated in .crt and also ca-bundle
together with the key i used to generate CSR, .crt and my key can match, but gitlab throw an error saying “Certificate misses intermediates”

if i try to import ca-bundle together with my key, gitlab throw below error
“Key doesn’t match the certificate”

I can see that my key and .crt is matched, no error
but im thinking my key would never match with ca-bundle right?

Question: How do I import this to Gitlab?

Thank you.