Android Question App signing error on Google Play

[stevetheframe]

Google Play asked me to update the target sdk to 28. I have done this, and uploaded the APK (signed with the only private key I have) to receive an error that the new APK is signed with a different certificate.
The only thing I can think of is that I have a new laptop, though I can't see that that would have an effect (the key file is stored on Dropbox).
Any help would be appreciated.

 

[stevetheframe]

Oops. Before embarrassing myself by putting my panic on the forum, I should have checked on the old computer where lo-and-behold was a second keystore file!

 

[Shelby]

Cool, that helps me too, remembering how many here and the instructions say keep that .keystore file so one can use it continually.