I recently built an app that plays sound files (.m4a and .mp4). It worked fine back in June this year. After the summer holidays, I needed to make some edits and found there was a new version of Thunkable. In this version, the sound files do not seem to work on the web preview. When I use the live test on device (iPhone 15) it plays the sounds fine.
There is no error on the web preview, I can see an icon in the browser showing me a file is being played, but I do not hear the sound. I have tried it on my personal laptop (Macbook) and work PC, both of which plays other sounds and do not have any sound issues. I know for sure that my Macbook played these files before because I developed the app on it. It only seems to be post this last upgrade.
Any suggestions or anyone else encountered this?
Since Thunkable upgrade in last 2 months, sound doesn't play anymore on Web preview but plays on iOS
Hi lisa.mendonsaxu, welcome to Thunkable! 
Be sure to check out How to ask Great Questions v2.0, the Community Guidelines, and our Getting Started Guide to make the best of your Thunkable Community experience!
Which browser do you use? Have you tried to use a different one?
I tried Safari and Firefox on my macbook. Safari shows the graphics but not sound. Firefox doesn’t even load the web preview!
However, inspired by your tip, I tried it on Chrome on a Windows PC and it worked perfectly.