It worked flawlessy since Update June 17 (on Firefox 77.0.1 (64 bit) Win10).
Now it keeps downloading feeds already donwloaded, read and deleted.
Before was 5 stars.
BTW thanks to the author and hope this extension will work again in the future. I'll keep it installed for a while.

Great assistance from Zakius! Problem solved, 5 stars
Tanks!