Sorry to hear that you have a problem with the Qksms. Usually, I don't send or receive videos, so after I read your comment, I tried to send a short video to myself, and it worked. Yes, I have Android 14 as well.
The root cause of your problem must be in the connection settings, or the video is too large.
If you can connect your phone to the PC and open Android Studio, select the log tab, and you will see everything that is going on in your phone's background. Now, try to send the video again. All errors related to that will appear as red text in the logs.
I hope you can fix it.
When someone writes to me in that way , first time gets a warning ⚠️ second time gets blocked 🚫.
It works out of the box without any other apps.