In 4D v17 R5, the OpenSSL version has been upgraded from v1.0.x to v1.1.x. This small change can cause an issue for some customers.
With this new version of OpenSSL the RC4 algorithm for certificate key generation is no longer supported.
Therefore if a customer migrates their database to 4D v17 R5 while still using an old certificate for HTTPS communications with the client, the connection will not be created. End users will be confronted with a blank web page.
In this case, the old certificate must be replaced by one that has its keys generated with a newer (supported) algorithm.