I've recently set my site up with Varnish full_page cache, and I have one specific URL that seems to be "stuck" and I am not able to clear it from the cache.
Last night I went into maintenance mode to do some updates, and this morning one URL is still showing the maintenance page, I guess because it got crawled while the site was down. All the other URLs I've tested are working but this specific one won't load.
This is production so I don't want to do anything crazy, I just want to clear that one page's cache and nothing I've tried works.
I have tried restarting Varnish at the command line but that does not work. Nor does clearing Magento cache on the front end.
I can disable full_page cache at the command line, and then I can see that the page loads properly. Then I restarted Varnish, and turned full_page cache back on, and the page then responded once again with the "Maintenance" page. So Varnish is hard-caching the page response, but how do I purge it?
Magento 2.3.2 and Varnish 6.0.3