ClassicPress 1.7.2 cannot enable sitemap

[aaro-n]

Introduction to the running environment

ClassicPress version: 1.7.2 PHP version: 8.0, 8.1 Database: planetscale XML Sitemap Generator for Google: 4.1.19

Problem description

I switched from WordPress to ClassicPress (1.6.5) in October 2023 and installed the XML Sitemap Generator for Google plugin. It was working fine until yesterday, when I suddenly noticed that the sitemap had disappeared. I went to the ClassicPress Settings and under Reading, I found that XML Sitemap Index was not checked to enable it. I checked XML Sitemap Index and saved it, but the page automatically refreshed and I found that the XML Sitemap Index that I had just enabled had disappeared. I repeated this several times with the same result.

Summary

Option	Can changes be saved?	Description
XML Sitemap Index	Changes cannot be saved	Checkbox disappears after saving and refreshing
Google News Sitemap	Changes cannot be saved	Checkbox disappears after saving and refreshing
Additional robots.txt rules	Changes can be saved	Content can be saved