So sorry for the inconvenience!
The first thing you should try to do is:
Finish the checklist
Try hitting Done at the Bottom of the screen if you are ready to submit.
If the system let’s you submit then you are fine.
After doing this, if you are still unable to submit:
Try to hit the home button at the top of the screen, this will exit you from the checklist and bring you back to your My Checklists page.
Don’t worry, all your answers are saved.
Then close the app completely
This varies on how it is done based on your device. With a computer browser you might just close the tab. On iOS and Android it is different.
Then open the app again, navigate back to your checklist.
Try Again. This should solve it.
If it is still an issues please continue and speak to a rep.