Faild to connect to host, Invalid namespace

Need more info @Asnex  What operation are you trying to perform? Are you installing Veeam? Trying to add vSphere or ESXi Hosts? Proxies? 

All server operating system Windows 2019 and Hyper-V Installed , not Proxies

Ok, so what operation are you doing and getting the error on? 

in Veeam Software : Microsoft Hyper-V   -    ADD to Server  -- Standalone Hosts

I'm typing the Server Ip I'm going to backup, I'm typing the Domain\admin password, when I say Next, I get this error.

Ah, ok. So you've installed VBR and you're trying to now add a Hyper-V host? Ok, did you review the Hyper-V documentation on how to add here and and made sure you meet the system requirements here? Without seeing everything you've done to this point, it's hard to say exactly the reason for the error. But I'd start with these docs first. Do you also have DNS in place or are you trying to just add by IP? 

Also, I assume you've installed the Hyper-V role on the server you're trying to add? 

Also, check out this post from last year where another user experienced the same issue. They didn't share explicitly what the issue was & what they did to get the 2nd Host to install, but we offered similar solutions for them. 

Hello
From the Veeam server, can you connect to the hyper-v server using \\<FQDN>\admin$ and \\<IPAddressofHyper-VHost>\admin$
 

I met this problem , it was cause by the UAC. Have you disabled it in the register base ? 

1. Navigate to HKEY_LOCAL_MACHINE > Software > Microsoft > Windows > Current Version > Policies > System
2. Double click on EnableLUA, verify if value is 0; if not, change it to 0.
3. Restart computer.

it gives an error in the  step 4 ( Specify Credentials)

I don't understand exactly what you mean. Our entire infrastructure is Hyper-V installed, where did you want me to install Hyper-V?

It's not the same problem, they have a problem with Timeout. not the same as me

I tried both, both are working and I can see all files.

Hi @Asnex ...I was just going off your error, making sure your HV role was indeed installed. Again, I don’t know the details of your environment so was offering suggestion based off what I could see by the info you provided.

So, did the registry change @Stabz suggested fix your issue then?

yes, but it still didn't work. What information exactly do you want from me?

Ah, ok. Darn. Hmmm...well, the only other option I can suggest, by the suggestions in the post from a yr ago, is to make sure you are typing in the username correctly. So, if you’re attempting to connect with a local account, make sure the username is in the format:  .\Username , then type the password. Or, if domain account: domain\username , then pwd. If that doesn’t work, I’m not sure of what else to try, besides opening a support case with Veeam.

First of all, thank you for your help. There is a domain in the environment Domain\Administrator and I tried it with .\Administrator as you wrote, it gave the same error again

Sure thing. Sorry wasn’t able to get you up & going though. The last option I can suggest is to get ahold of Veeam support to see what they find.

Maybe a problem with the DCOM, I supposed your Windows are up to date?
See KB: https://www.veeam.com/kb4376