Failed to restart redis.service: Unit redis.service not found in Ubuntu

Hello guys, I have a Linux Ubuntu 20.04 and installed a Redis server. Today I restarted the server but Redis server stopped and I tried to restart it by using command sudo systemctl restart redis.service. But I got an error:

 Failed to restart redis.service: Unit redis.service not found.

I tried to reinstall Redis by using the command sudo apt install redis-server. But I got the error:

 Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
redis-server is already the newest version (5:6.0.16-1ubuntu1).
The following package was automatically installed and is no longer required:
  ltrace
Use 'sudo apt autoremove' to remove it.
0 upgraded, 0 newly installed, 0 to remove and 5 not upgraded.

I also tried to check the status of the Redis server by command sudo systemctl status redis. I also got an error:

 Unit redis.service could not be found.

I feel I can't do anything with Redis. Anyone can enable it to help me.

Thank you in advance.