The Custom Field tag association system is only designed to associate a Custom Field with 1 tag group and NOT multiple tags.

Please click here to view a short video on how to associate a Custom Field with a Tag. 

Please see a screenshot below of an example of Custom Fields linked to 1 tag group: 

Why your MUST not associate more than one tag group to a custom field:

The issue with creating a custom field which is set up 'once' inside Global Settings and associated to more than 1 tag group is that information WILL duplicate if the contact has these same tags applied to their record. 

To avoid this issue, the custom field should be linked to only 1 tag group at a time - if needs to be linked to more tags the custom field must be repeated and linked to one tag at a time.

As an example if you had a custom field called 'Location' which you applied to several different tag groups then if a contact record was tagged with these several different tags the field would repeat and duplicate the information entered in one field - into all the other 'Location' fields. 

It is difficult therefore to 'isolate' data.

To discuss the setup of your Custom Fields further please contact our Support Helpdesk.