First, sorry for my english i am french

We have vsphere's servers.
In february, the mensual backup crashed.
I reboot services, and services crashes too.
I reboot 2x the veeam server and problems are the same.
I delete the mensual job.
I create the new mensual job and i noticed the server veeam can't contact vsphere.
I reboot services on vsphere and same problem.
So, i reboot vsphere ans after, the mensual job worked !
But, today, i would like to restore a file to January, but a i have an error "cannot retrive mount result. File does not exist" ... He can't found the january's .vbk ...
I went to see to the folder and i have only files .vib
so, why my .vbk disappeared ??
Thanks a lot !