docs:cdiwadkar16-patch-4-68 - changed link

from FQDN blog in Chinese to FAQ section.

docs-en/14-reference/03-connector/csharp.mdx

@@ -179,7 +179,7 @@ namespace TDengineExample
 
 1. "Unable to establish connection", "Unable to resolve FQDN"
 
-  Usually, it cause by the FQDN configuration is incorrect, you can refer to [How to understand TDengine's FQDN (Chinese)](https://www.taosdata.com/blog/2021/07/29/2741.html) to solve it. 
+  Usually, it's caused by an incorrect FQDN configuration. Please refer to this section in the [FAQ](https://docs.tdengine.com/2.4/train-faq/faq/#2-how-to-handle-unable-to-establish-connection) to troubleshoot. 
 
 2. Unhandled exception. System.DllNotFoundException: Unable to load DLL 'taos' or one of its dependencies: The specified module cannot be found.