0 - The request was successfully processed by API2Cart 
1 - Service not available
2 - Incorrect API Key
3 - Method is not specified
4 - Store access denied
5 - API access denied
6 - API Key is disabled
7 - Store request limit exceeded
8 - Store already exists
9 - Internal service error
10 - Account request limit exceeded

100 - Store API access error: incorrect URL, resource is not reachable or API credentials not valid
101 - Store not found
102 - Incorrect FTP access (see details in return_message)
103 - Incorrect FTP write permissions
104 - Wrong ftp_store_dir, can’t find a bridge
105 - Connection Bridge response error (see details in return_message)
106 - Store URL is not reachable
107 - Uncategorized error received from the store
109 - Incorrect parameters for “method_name” (charset etc.)
110 - Too many requests to the store's API
111 - Too many items requested (product, variant, etc.)
112 - Item not found (product, category, etc)
113 - Entity already exists
114 - Required parameter is not specified
115 - Too many possible prefixes (more than one)
116 - Duplicate record in database