I think there is some error with the website today. I cannot insert any images either. Ansys staff cannot download attachments or open links in the student community, so it will help if you can insert images (maybe try it tomorrow).
Based on the description you gave, I would suggest the following things as your initial trials:
1. Try setting the max and initial substep as a large number (like 1000). The reason may be your initial substep is too large.
2. If your shell elements have buckling model, try add some nonlinear stabilization (It is under analysis settings). You can start with the energy ratio method, and use a small value 1e-4, if doesn't work, you can slowly increase the value. But be careful the artificial energy added is not too large.
3. In contact settings, turn off "Trim contact"