I cannot drag photos into a cell when using custom packages in the print module. Is there a setting I disabled?
Would suggest you to reset the Lightroom Preferences.
Before you reset, make sure you know the location of your main Lightroom catalog which can be checked by going under Catalog settings> General
Refer this article to reset preferences : https://helpx.adobe.com/lightroom/kb/recover-catalog-images-resetting-lightrooms.html#id_9 0046
If that does not help, would suggest you to provide the following information :