Rests in bass clef

By replacing them with notes. Please post your score so we can look at it. Take a look, too, at https://musescore.org/en/handbook/voices .

A common mistake is to skip voice 1 in the bass clef clef staff of a piano or SATB score. Don't do that. Each staff needs to start with voice 1.

It's also possible you are using cross-staff notation, so you have a situation where the notes of one staff appear in the other and you need to manipulate the rests specially. "V" will toggle visibility of rests or anything else in those unusual special cases. But best to attach your score to be sure.