Tags Suddenly Stopped Working?

I run a large blog via Squarespace: https://www.tobedetermined.cc

We use tags heavily for organization purposes. But within the past couple of weeks, the majority of the tags that we use effectively disappeared: (1) they do not appear under "Manage Tags" when going to the blog settings (2) many of them appear as dead links, i.e. when clicking the "Apparel" tag on this post (https://www.tobedetermined.cc/journal/castelli-unlimited-cargo-bibs-review-new), rather than opening related blog posts, it pops a bad link error, and (3) only a handful of tags show up in our main tag cloud, most of them associated with very old blog posts - there should be more the maximum of 100 tags listed here: https://www.tobedetermined.cc/topics

Any ideas on how to fix? The tags are across hundreds of blog posts so I cannot go back and recreate them all.