First of all, thank you very much, Anke.
Upon reviewing, I noticed that I had the app name wrong because I had uploaded it with an "_11" added. This generates the zip with the private key, but it tells me that it does not correspond with the current certificate.
Here I get lost with the .jks files; it seems to ask for a previous one and a current one.
I also tried uploading the APK directly because it is from before August 2021, but it also gives a certificate error (logically).
Best regards.