Campaign map (layout) and slides no longer available. Plus problem with the thumbnail

I have two isasues:

  1. I have made a second version of my campaign, but this time the slides and the campaign map longer available. Haven’t changed anything. How do I solve this?
  2. I try to upload a second campaign, but I get a message that says “missing thumbnail”, even though I have a thumbnail, every time I try to upload the mod, the thumbnail dissapears from the file…
    How do I solve these problems???