Hello @almahmoud,
This looks to be like a plugin conflict. Do you see any browser console errors? If not, could you take a site backup and disable all other plugins and then enable just the forminator plugin and check if that works? If it does, go ahead and enable plugins one by one and check the drag and drop function on each activation.
The moment drag and drop stops working, that is the conflicting plugin. You would need to check with that plugin author them to let them know about it so they can help you fix it.
If any of the above does not help, could you help me with the forminator version, WP and PHP version on the site to try and replicate the same on my end?
Thank you,
Prathamesh Palve