Trouble changing the header

I am having trouble changing the header for my site. When I click on change the header in the customize section and select the image I want from the media gallery then click on select and crop there is no button to click on to insert into the header as there usually is.

Hello there,

That such kind off issue happens because there might be a plugin produce a JS conflict on the customizer panel. What will happen if you try to temporarily deactivate the all non-required plugins? You would need to clear your browser’s cache before visiting the customizer panel.

Regards,
Kharis