Hello,
Thank you very much for choosing our theme and for contacting us.
Please deactivate all the plugins not related to the theme and switch the parent theme, check the issue, If the problem has gone, activate the plugins one by one, checking the issue to detect which one causes the problem.
if the problem remains, even after the plugins deactivated, disable mod_security
on your server. It seems to block Header Builder’s “save” requests. Contact your hosting provider for help on this matter.
Best Regards