Minor Playback Issue Involving Tied Notes In Musescore 4

MuseScore 4 is not released yet.
If you are using an alpha, beta, nightly, self build version, etc. of MS 4, see:
musescore.org/en/forum
and look for a forum titled Development and Technology Previiew
“Discussing the developing MuseScore and the development builds…”

To me, that seems more like the place to post. Most folk here are still using version 3.

If you read the announcements for MuseScore 4, the recommended place is GitHub:
“We strongly prefer issues to be reported on GitHub until we release MS4 (this requires a GitHub account): github.com/musescore/MuseScore/issues
Alternatively, you can submit any issues you find on our issue tracker: musescore.org/en/project/issues/musescore“

To your issue, you wrote:
The only way I’ve found to get both notes to play is to untie them to the next note.
See:
musescore.org/en/handbook/3/slurs
and:
musescore.org/en/handbook/3/ties
This is from the MS3 handbook, but it explains the difference and why untying plays the next note.