Cannot generate an XML sitemap!

When you tried to generate a sitemap, what kind of 404 error page did you see (a screenshot might help)?

Edit: Double post sorry

It was my theme default 404 page: Oups, this page cannot be found ?? (and my theme displays)
https://i67.tinypic.com/9a7hu8.png

Can you try removing these two lines:

sitemap(_index|[0-9]+)?\.xml
sitemapindex?\.xml(\.gz)?

from W3TC’s “prevent caching exception list”?

I don’t remember to ever recommend doing that in the FAQ.

One last thing to try if you haven’t done so already: https://betterwp.net/wordpress-plugins/google-xml-sitemaps/faq/#rewrite-rules-error

Thank you very much, I have checked the link your provided me and followed those steps:

404 / Not Found Errors
When I visit https://example.com/sitemapindex.xml, I see a WordPress “404 / Not Found” page. What should I do?
This might be caused by unflushed rewrite rules, which should have been flushed when you activate this plugin. You can try flushing them manually by visiting Settings >> Permalinks and then clicking Save Changes.

That fixed the problem for me, thanks!

Glad you got it working.

Are you using multisite? You should not have this issue if you simply have one single blog.

Also, had W3TC been activated before you installed BWP Sitemaps?

No, I use only one site
Yes, I did install & activate w3 before using or installing BWP

I just wanted to flag up that I use this plugin on lots of sites and have had no issues with it at all until yesterday. I too got the page 404 error. I have just turned it on in another (single) site and the same thing happened which is why I came to here. I followed the instructions above about deselecting and reselecting permalinks and saving. That cleared it in my case. So thanks for that. However I use this on 70 sites and it was worked without any problems so sounds like there is a bug in there somewhere. Thanks for building and supporting the plugin.

@wingers574 thanks for reporting. Was there any change you made to your site yesterday, such as installing new plugins?

In the first case I added in the plugin which I normally do and then enabled it and clicked on the site map generation link. The other plugins I use are generally the same on all sites which is why this behaviour is a little odd. In the second case, it was already installed/ updated and the sitemap generation link caused the 404 error. I removed the plugin, added it back in again, changed the permalinks setting and changed it back again (as a result of reading this thread) and it all worked ok. I can give you a list of the plugins I typically use, however I suspect that because it can be resolved by clearing something (I don’t have enough knowledge to know what), I suspect it is something within the plugin that may be causing it. Commenting wholly from a position of ignorance :-), I only know this problem existed because I install it and set it up in a basic configuration. So I only click on the sitemap generator link once. I never touch it after that. An interesting test would be to go to another site where it was installed without any issues and click on it again to see if it creates the 404 error.

… in answer to the last question. I just visited an established site with an established sitemap and clicked on the link to generate a new site map and the page 404 error did not occur. So it is behaving normally.

@wingers574 thank you for all the details. I would like to know the list of plugins you’re typically using, or more specifically ones you’re using on site that you encountered the 404 not found error.