When I go to attempt to edit a tag wiki, it redirects me to this page:
The tag definitely isn't deleted and it's also not a post as this words it. What is going on?
Your edit ban is temporary, and will be lifted automatically in about a week or so. In the meantime, you can review your suggested edits and any rejection reasons on your 'All Actions' tab on your profile. This should at least give you a reason as to why your edits were being rejected.
Note that the community is a little more stringent when it comes to tag wiki edits (when compared to Suggested Edits on questions and answers), so make sure any edits are substantial and actually improve the wiki/excerpt. A few years ago as part of a larger cleanup effort, the community decided on a format for Tag excerpts and Wikis that works well for us so have a look at this question and the answer for some guidance: How should I write tag wikis?