Q:

Mobile Connect Import

I am trying to subscribe back the contacts in Mobile Connect who have status as 'Not Opted in' through a csv file.  However, the import says 'Invalid Context Status'.  Does this mean that we cannot update a mobile subscriber's opt in status through import file? 

A:

Looks like you cannot opt-in via bulk import when contact is opted-out. 
The only way to opt them back in is via SMS or via API. 
ref: (Is there a way to update MobileConnect Subscription Data from a Data Extension?) 
API call Example:
PATCH /contacts/v1/contacts
Host: {{subDomain}}.rest.marketingcloudapis.com
Content-Type: application/json
Authorization: Bearer {{authToken}}

{
   "contactKey":"1234",
   "attributeSets": [{
         "name":"MobileConnect Subscriptions",
         "items": [{
               "values": [
                     { "name":"Keyword", "value":"XXXXXXXXX" },
                     { "name":"Mobile Number", "value":"15558675309" },
                     { "name":"Opt In Status", "value":1 },
                     { "name":"Opt Out Status", "value":0 }
               ]
         }]
   }]
}

