Nimbostratus
MVPMahdi_Moradi Without seeing more of your configuration it makes it a bit difficult to help with the solution. If you only had one server in rotation before and you are adding this new one as a redundant host I would guess that you have an issue with persistence or persistence across services. I would ensure persistence across services is enabled and see if that resolves your issue.
Nimbostratuspersistence none
pool config : 1 node , ip adddress port : all port
vs : dast add , port :30112 -- auto nat -- porofile http -
config is default