Your slide isn't where it needs to be.
What likely happened is when you reinserted the slide stop you didn't get it through the cam hole in the barrel... that's pretty common with new users in both the P938 and the P238.
To fix, pull the slide stop out. Then, reinsert:
1) Put the slide back on the frame. Be careful to push the ejector down to clear the slide, but DO NOT push it down too far.
2) When the slide is in its proper orientation (back of slide flush with back of frame), insert the slide stop through the cam hole in the barrel... you should be able to see this get into place through the hole. Note that you can't push the slide stop all the way home at this point.
3) With the shaft of the slide stop sticking through the cam hole in the barrel, pull the slide back so the takedown notch is in the proper location to fully insert the slide stop. Then insert it all the way- it should push right in.