Problem 

When trying to connect to FC Server with the FC Abbyy Mobile app the following error message appears: 

An error occurred during authorization.
Java exception: com.google.b.d.d: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1 path $

Solution 

To connect mobile clients to the server, basic authentication is used.
Please, check if basic Authentication is enabled in IIS in the Login folder: <app server name>\Sites\Default Web Site\FlexiCapture12\Login:


As well as in the Server

1. Try to use just http://<IP>/ in the URL field without /FlexiCapture12 
2. Leave the"Company"field blank (If you use Tenant, you may enter its name in this field)
3. Instead of Domain\Username in the UserName field, please try to use just the username