Disabling the CDN doesn't work

I’m using MathJax-LaTeX 1.2.1, having just migrated from 1.0.

Problem: un-checking “Use MathJax CDN Service” does not work at all.

I had to run this MySQL query to disable it:
INSERT INTO wp_options (option_name, option_value) VALUES ('kblog_mathjax_use_cdn',0);

It seems the checkbox is simply not getting saved.

Thanks!

https://www.ads-software.com/extend/plugins/mathjax-latex/