Please only to people with real back-end Java development experience for API/REST.
I'm an old generation programmer, with zero Java knowledge. The aim of this question is to be introductory on how Java works with certificates, how to debug and solve, not necessarily on coding.
Jumping into the thing...
My Java app communicates with the Tax Authority servers for data exchange.
I only have a production environment, so I can't really take much risk of crashing my app.
I have my pfx file, and it works perfectly in Windows outside of my Java app.
The pfx file is used to handshake with those servers. With the handshake, I receive two strings of text (a "token" and a "sign"). With that token & sign, I can consume the web service freely for 12 hours. Meaning: I only use the certificate every 12 hours to obtain a token and a sign. This is managed by an automated procedure, I think the name is Cron, in Linux.
(The Windows way, is another way to make "the handshake" outside my server)
Every year, when I renew the pfx file with a new certificate I upload it to the server /home/xxx/*.pfx and replace the old one
After replacing the file the "handshake" described above, the Cron process fails. In the past, the developer solved this, but he is not available anymore.
The kind of help that I'm looking for is for someone with Java API experience to guide me on how to solve it, so I can learn its "how to".
How can I begin to debug what might be happening with my app?
As I was able to research, I'm having some thing related to the Java keystore, or/and certificate signature.
Something like, obviously, uploading and replacing files are not enough.