Certificate file an not import on iPad -- iOS13

I had Installed Sophos Network Agent (iOS version)  on new iPad.
However, certificate file downloaded from Sophos XG450 user Portatl cannot be imported.

When I checked the information in the certificate file, it was related to "Scenarist Closed Caption".

Cause the file name is ClientAuth_CA.scc, and the extensions linked to ".scc".

Troubled iOS 13.1.1 (7th generation iPad)
Certificates can be imported without problems on elder versions of iOS 12.4.3 (iPad Air).

The file relationship can change  on Mac OS at Finder, but can not change on iPad (iOS).

How do I import a certificate?