Fermatas on bar lines don’t appear at instrument changes — presumably because the barline is the new instrument but the fermatas is technically in the previous measure.
On the place where I am, I don’t have a pc, so I can’t test it here, but perhaps this is a solution: place the carrot 1/32 before the barrow line and place there the fermata. In the engrave tab you can adjust the exact place for the fermata. I hope this helps.
This is definitely one way of dealing with this. What I actually did is instead of doing an actual instrument change I just kept it all in one instrument. But I mostly just posted this on the off-chance that this was not a known issue.