SVN commit fails

I’ve checked the posting rules, and I’m pretty sure this post fits them all.

I have a plugin in the WordPress repository. I’m the only developer. I’ve updated it several times the last few years. Now I can’t. My old SVN program (svnX) no longer seems to work, so I’ve moved to SmartSVN.

While I can browse the repository and checkout files in my plugin, I can’t commit any changed files. Each and every attempt ends with “Access to ‘/!svn/me’ forbidden”. I’ve tried http and https, I’ve double checked the case of the url, I’ve done everything I can think of. I really need to get these updates into the repository.

SVN sucks.

Here are a couple of relevant lines from the SVN log:

276314 (2018-01-29 08:34:05,027) [WorkerThread-3] ERROR smartsvn.runnable – URL access forbidden for unknown reason
svn: Commit failed (details follow):
svn: Access to ‘/!svn/me’ forbidden

Any advice would be appreciated.