rick, what versions of EE and Sitemap are you on? my first piece of advice would be, if you can, to reset the publish layout for the channel that is giving you issues.
Ben; I’m using EE 2.9.2 and Sitemap module 2.6.4. I followed your advice and tried resetting the publish layout for one of my channels. At first I thought that the reset function wasn’t working, until a bit of googling revealed that one needs to refresh the browser window in order to see the reset. (That’s not mentioned in the EE docs AFAICT so I’m mentioning it here in case it helps others). So the reset worked.
Then I thought that there was as a further issue with Sitemap Module, because the Sitemap tab disappeared altogether. This foxed me for a minute until I realised that the channel upon which I was testing the ‘publish layout reset’ was one of the ones that I’d excluded in the Sitemap preferences and replaced with a ‘location’ as per your advice here .
So I tried the same layout reset process with a channel that was included as a channel in the Sitemap prefs, and it worked. The Sitemap tab is still there and now the ping checkbox is visible.
BTW, out of interest I created a new test channel. Upon going to the publish page the Sitemap tab was fully functioning. So the issue seems to be with channels that had publishing layouts set/saved before Sitemap Module was installed. They need to be reset. (Unfortunately that means that I now need to reset and recreate every one of my publishing layouts, but I guess it can’t be helped).
Thanks for the advice, anyway; it’s solved the issue. But maybe there’s something that can be done inside Sitemap so that this isn’t necessary, ie. existing publishing layouts don’t break if Sitemap is installed after they are created)?