12:35:21 AM Task failed. Error: Connection problems.

A lot more details needed here to be able to provide meaningful answers. What are you doing? Backup? Replication? Restore? Failover?

What is it that fails exactly in that job? Application aware processing?

Thank you for your replay. Daily backup, it was working normally 10 days ago, but the last five days have been plagued by this issue.

Operation system: Windows Server 2019,

Server type: physical server.

Any logs and/or screenshots you can share?

Is it Agent backup or VBR backup? Any screenshots you can provide would help. Also, you can view log files in C:\ProgramData\Veeam\Backup and look for the name of the job or server name 

Here is an enclosed screenshot.

I tried, but it’s not working.

Can you ping your physical host? 

Yes, I can ping.

Ok great. Can you Admin share to the server using the same credentials as in your Protection Group? 

I tried also and am getting the same problem. I tried a new agent backup.

I am getting the below error.

1. Waiting for rescan job Rescan of Agent Backup Job 11 to complete     01:00
2. Unable to process 10.0.14.1: host rescan is required
3. Nothing to process
4. Job finished with error at 9/21/2023 1:25:39 PM 

Veeam agent was installed, but I tried to install the Veeam CBT Driver, but it failed.

21/09/2023 1:36:55 PM Succeeded Processing com 
21/09/2023 1:38:09 PM Succeeded com state updated 
21/09/2023 1:39:14 PM Failed [Srv] Failed to install Veeam CBT Driver: Connection problems. 0:01:00
21/09/2023 1:40:20 PM Succeeded Backup agent is installed 

Can you Admin share to your server? In file explorer, on the address bar, type in \\hostname\c$, then enter your credentials to connect. If you can, great. If you can't, then there's the issue.

Also, are you using a local account to connect or a domain account? 

BTW, whether you're using a domain or local account, the username syntax is: DOMAIN\user or HOST\user, then the password 

I tried to check the address bar; type in \\hostname\c$.

I am getting the error I gave below.

When I tried it with an IP (\\Ip Address\c$.)address, it was working.

Ah, ok. So there’s your answer @Antony_cm . Your DNS isn’t working properly if you can connect via IP but not hostname. This server obviously doesn’t have a DNS record. Are all your machines → VBR server and this “Dell-x” server, on the domain or in a “workgroup”? (local devices) If they are not on a domain, and there is no DNS server, you have to enter hostname and IP information in each server’s hosts file , located at:
C:\Windows\System32\drivers\etc\hosts .

Otherwise, you’ll just need to use the IP of the server to connect to it.

This link can assist you, if you need to modify your local hosts file manually. Before you modify it, make a copy of the original so you have something to fall back to in case you mess something up.