Exiting Customizer alert

Question

I get an browser alert when exiting Customizer that my changes will be lost if I navigate off this page. Everything is saved in customizer, so when I navigate back to it, it shows the logo and everything, but they aren't on published pages outside customizer. I've checked that customizer settings are Published. I've installed wordpress a new with blank database and it still occurs. Using twenty seventeen and blank underscores_me themes here. Happens on both. Css works ok, like the background image I've placed. I haven't found any info on this.

I haven't got any plugins active and the two that are installed came with wordpress 4.9.8 package.

Is this a server problem? WP-CLI problem?

Answer 1

Please try this. Open your website in Google Chrome, open the DevTools window (using F12), and switch to Console tab. Then try opening the Customizer and try saving changes. Do you see any errors?

Also, if you switch to the Network tab on DevTools and filter by XHR, do you see any ajax request that have an error? If so, can you inspect that and update your question?

If everything is fine on the DevTools, you should check the PHP version of the server. If it is lower than 5.4, there is high probability that this is the cause. Nothing else comes to my mind.