Generally, PFX files are generated without a password. When importing and being asked for a password this can normally be left blank. Some systems insist that a password is entered.
Therefore we recommend regenerating the PFX file with a password. This can be done using OpenSSL
First convert the PFX file to PEM.
openssl pkcs12 -in cert.pfx -out cert.pem -nodes
Then convert the PEM file back to PFX and specify a password
openssl pkcs12 -export -out cert.pfx -in cert.pem
Enter Export Passord:
Verifying - Enter Export Password: