This issue occurs when you try to import the certificate under 'Your Certificates' tab. You should be importing it from Authorities tab. Please follow the steps below to import the certificate, once they are downloaded.
1. Go to chrome://settings/certificates
2. Click on 'Import' in the path - Certificate Manager > Authorities
3. Select the downloaded certificate and click open.
4. Choose the option 'Trust this certificate for identifying websites' and click Ok.