Settings do not change

Using latest plugin version, WP 5.3.2, FireFox 72.0.1, single site (although also happens on multisite). No ad blocker active.

On the Settings screen, changing anything does not save. There is no action that happens with the ‘Save’ button. The screen does not refresh, there is no message that settings are change, the new setting is not shown on the screen.

This has happened with prior versions, and is happening in multiple WP installations.

Refreshing the screen will appear to have the new setting. But going back to the dashboard, then back into the Settings screen will show the old setting.

On a multisite system, the only way to make permanent changes is via the SuperAdmin, site settings screen. But that is not available in single-site installations.

Again, this has been happening for several versions of the plugin.