What happens if you dial manually?
I had had Google Contacts set up for years using the +18005551212 format. Suddenly, in the middle of the day, I could make no calls or send texts using shortcuts or contacts. I finally determined the + sign was causing my S3 to not dial out. I modified all of my contacts to remove the + sign and everything is fine. Took me awhile to figure out, since it was so random and it happened in the middle of the day.