Groups are removed from contacts whenever a CSV file is uploaded to Everbridge Suite.
Specific syntax is required when uploading contacts so that contacts are not accidentally removed from groups. One cause of this problem is when there are blank values under the Groups header column in the upload file. Uploading a file with any fields under the Groups header having a blank value will "blank out" the data for that field for that contact. For example, if the Groups header in an upload file has all blank values, then all contacts affected by the upload will be removed from any groups.
Another cause of this problem is when the asterisk ( * ) character is not properly used in each group cell to preserve existing group associations.
If you are not managing groups in the upload file, do not include the "Groups" column in the upload file.
If you are managing groups in the upload file, see the following references:
Knowledge Base Article 000048620 - How to Add Contacts to Groups via an Upload File for information on how to preserve existing group associations when uploading contacts and how to safely add/remove contacts to/from groups without deleting existing group associations.