No sound

Hi,

I have installed the cinnamon version of Workrave from the PPA to my
Linux Mint 19.3 machine. Everything works fine except for the sounds.
There are three options offered in the settings: Sound card, speakers
and no sound.

Number one give me the options to listen to the sounds and choose
between Classic and Subtle, but when I play them, I hear nothing.

Number two has everything greyed out, but maybe this is intentional,
since I have read that this option will be removed in the future anyway.

Number three obviously does what it says ;-)

I use external speakers on my computer, and they work audibly, and the
test in the sound settings is passed as well.

Do you have any suggestions to fix this issue or is this a bug?

Thank you for your help and thanks for the great software.