Hey there,
I have checked your database and it seems like some of the user id's are out of sync. In EasySocial's avatar table, there are already data for user ids of 100,101,102,103,104,107 . However, upon registering a new user on your site, the id is 100 and 101.
Did you actually migrated the data but did not migrate the users? To fix this I had to delete all these records that are above the current id which is anything above 102.
When registering now, the default avatar is showing up correctly.