First please check you’re running the latest version of iOS and update your software if you’re not.
After that, please try logging out of the app, then closing the app (double click the button on your front screen and swipe the app upwards until it disappears).
It would also be helpful to close all the other apps you have open. They can sometimes cause glitches or a lack of space for the pods on your system.
Finally hold the front button and top button together past the point where the off switch appears, until the Apple symbol appears. This can take about 10-15 seconds, then another minute or so to reboot your system.
Then open the Slimpod app and log in again. This should clear out any glitches that you have.