Resolve C# Connection Issue "StackExchange.Redis.RedisConnectionException: No connection is active/available to service this operation: It was not possible to connect to the redis server(s). There was an authentication failure; check that passwords (or client certificates) are configured correctly." to Azure Redis cache Connection via Private Endpoint

 Using Azure Redis cache with C# throws an error message such as below while accessing the Redis cache via a private endpoint.

StackExchange.Redis.RedisConnectionException: 

No connection is active/available to service this operation: 

GET Zdddddddddddddddddddddddddd; It was not possible to connect to the redis server(s). 

There was an authentication failure; check that passwords (or client certificates) are 

configured correctly. ConnectTimeout, mc: 1/1/0, mgr: 10 of 10 available,

 clientName: DESKTOP-XXXXX, IOCP: (Busy=1,Free=999,Min=16,Max=1000), WORKER: 

(Busy=3,Free=32764,Min=16,Max=32767), v: 2.2.88.56325
 ---> StackExchange.Redis.RedisConnectionException: It was not possible to connect to the 

redis server(s). There was an authentication failure; check that passwords 

(or client certificates) are configured correctly. ConnectTimeout
   --- End of inner exception stack trace ---

This could be due to using the connection to Redis cache as below with privatelink in the connection string.

yourrediscache.privatelink.redis.cache.windows.net:6380

Using the connection without privatelink part as below would solve the problem and you would be able to connect to Azure Redis cache via the private endpoint.

yourrediscache.redis.cache.windows.net:6380

For further information see the answer here.