cannot add categories in product edit screen for existing products

[yakir_yakir]

in product edit page, existing product categories can be unchecked, but the rest of the categories cannot be checked -- which means i cannot add product to categories from product edit page.

once i uncheck a category, and save, it is grayed out and cannot be checked again.
there is an exception, i can add new products to any category, but once the product is listed i cannot add it to new categories from product edit page.
i can though add products to a category from category edit page.
 magento 1.9.0.1
anyone who can help? thanks!

[yakir_yakir]

once i uncheck a category, and save, it is grayed out and cannot be checked again.
there is an exception, i can add new products to any category, but once the product is listed i cannot add it to new categories from product edit page.
i can though add products to a category from category edit page.
 magento 1.9.0.1
anyone who can help? thanks!

[Sarvagya Pandey]

Hello @yakir_yakir,

I think the issue could be in AJAX and permissions. Please check your server error log that will provide you some hint regarding the error.

Does your hosting have any security type software on it that attempts to block rogue requests? It may be worth having a word with them (and sending them the 403'ing url) to see if they can shed any light on it for you.

Or else try reset permissions, probably some files just lost their execution bit:

find . -type f -exec chmod 644 {} \; 
find . -type d -exec chmod 755 {} \; 

I hope this will help you. If still you face any issue, let me know.

If this helps you, please accept it as solution and give kudos.

Regards.