Problem
The category is grayed out because it is deactivated.
Solution
If a category appears grayed out in Pricebook, locate the category and edit to reactivate it.
Find a deactivated category
Note: Ensure you have the Edit category permission enabled to edit the grayed out categories. If you don't have the permission, please contact the account administrator on your team.
Go to the navigation bar and click Pricebook.
In the side panel, click Categories.
Click Filters, for Status click Inactive to see only inactive categories.
Click Apply.

Find the category and click Activate
. 