If you have a lot of media assets or if each one is a particularly large file, it can take a long time to import each one and the page will appear stuck even though it’s working. Without knowing the number and size of your files, I can’t say for sure, but that’s the most likely culprit.
That’s helpful context; thanks! If it’s been a while since you’ve cleared your browser’s cache and cookies, you may want to try that as well. Sometimes if you haven’t done this in a while it can cause websites to not behave correctly.
If you run into this again, send the files over to services@wildme.org so we can do additional testing.