Add the repository or download the RPMs from the repo

#RHEL 6:
wget http://repository.veeam.com/backup/linux/agent/rpm/el/6/x86_64/veeam-2.0.1.665-1.el6.x86_64.rpm
wget http://repository.veeam.com/backup/linux/agent/rpm/el/6/x86_64/kmod-veeamsnap-2.0.1.665-1.el6.x86_64.rpm

#RHEL 7:
wget http://repository.veeam.com/backup/linux/agent/rpm/el/7/x86_64/veeam-2.0.1.665-1.el7.x86_64.rpm
wget http://repository.veeam.com/backup/linux/agent/rpm/el/7/x86_64/kmod-veeamsnap-2.0.1.665-1.el7.x86_64.rpm

#install via 
yum install veeam-2.0.1.665-1

#or 
rpm -ivh veeam-2.0.1.665-1 kmod-veeamsnap-2.0.1.665-1

Start Veeam via “veeam” and enter “C” to open the configuration

You can backup your configuration via the following command

veeamconfig config export --file /root/veeamconfig-2019xxxx

and import an existing configuration via

veeamconfig config import --file /root/veeamconfig-2019xxxx
  Current configuration will be overwritten. Import anyway?(yes/no): yes
  Type in password for username: svc_veeam and address: srvbck: <password>

You updated to version 3 and now the agent is incompatible to your repository. Therefore you need to downgrade back to version 2. Running your job in the downgraded version fails because of the veeamsnap module.

Reason:
The module isnt fitting your kernel

Fix:
Execute the following to downgrade successfully

#List the current installed packages
rpm -qa |grep veeam

#Remove the packages
rpm -e veeam-<version> veeamsnap-<version>

#Clean reinstall (veeamsnap will be installed as dependency)
yum install veeam-2.0.1.665-1.el6.x86_64 

#or

rpm -ivh veeam-2.0.1.665-1 kmod-veeamsnap-2.0.1.665-1

#List the module
dkms status
   veeamsnap, 2.0.1.665, 2.6.32-754.11.1.el6.x86_64, x86_64: installed (WARNING! Diff between built and installed module!)

#Remove the module, rebuild and force install it
dkms remove -m veeamsnap -v 2.0.1.665 --all
dkms build -m veeamsnap -v 2.0.1.665
dkms install -m veeamsnap -v 2.0.1.665 --force

#open "veeam" and edit configuration via "C"

Veeam Agent Linux