Google Play allows the ability to reset your signing cert for uploading now with them optionally managing the release certs. You contact them with new certificate in case you lose yours if you opt into this feature.
I was testing this reset process - only took 1 day to get a reply from them. Here is what they said based on a pem generated with the steps listed in the docs here Defold development for the Android platform
Here is what update e-mail from Google looks like after you do send correct certificate:
Hello,
We received a request to reset your upload key for _. The new upload key will become valid on Dec 20, 2017 at 8:56 PM GMT. Until the new upload key becomes valid, you can’t upload any new APKs.
New upload certificate fingerprints:
MD5: 85:AB:6C:8C:DF:BD:91:11:1C:08:B8:16:8D:53:4B:FD
SHA1: 3C:91:F8:23:BA:AC:BF:2E:D6:D9:2A:0E:55:16:60:B3:3E:7B:8E:E4
If you didn’t request a reset, let us know.
Sincerely,
The Google Play team
So apparently once a certificate is accepted it takes ~2 days for it to be usable for uploading new apks. 3-4 business days for whole process assuming correct certificate is sent in the first place.