Call recorder records Empty - 3gp files

Maybe a problem with the Call Recorder app itself?
But as it's sideloaded from Uptodown, could be it's incompatible with your particular phone or tablet? Try installing it directly from Play Store instead?

Of course I'm not going to try this app, no need as my phone can record phone calls.

 

what phone do you have?

 

This can be a problem if the Uptodown website is used, but if the Uptodown app is used instead, it will download the correct versions of apps for whatever device.

The app itself is actually quite nice- small and efficient.

It can do the majority of what Google Play Store can do, as far as alerting of updates, malware protection, and getting the right versions of apps.