If you source GCP key from .pem file and upload it then the account will show healthy, but won't pull in costs.
The .pem file needs to be converted to PKCS8 first. You may refer the stackoverflow articles below
https://stackoverflow.com/questions/8290435/convert-pem-traditional-private-key-to-pkcs8-private-key
https://stackoverflow.com/questions/20065304/differences-between-begin-rsa-private-key-and-begin-private-key/20065522#20065522
You can also use openssl
openssl pkcs8 -topk8 -inform PEM -outform DER -in filename -out filename -nocrypt
# openssl pkcs8 -topk8 -inform PEM -outform PEM -nocrypt -in pkcs1.key -out pkcs8.key