can't access web admin for vesta, Unit vesta.service could not be found.

[ahmed]

Hello,
i'm facing a strange issue on couple of servers supposed to be running vesta
OS: centos 7
suddenly i can't access vesta admin on both of them, although nginx websites are up, thats the only thing working.
i thought its just a simple service or server reboot, but seems like its not.
when i try to "systemctl status vesta.service" i get "Unit vesta.service could not be found."
also "v-restart-service vesta" throws "Error: vesta restart failed"
on var/log/vesta/error.log i can see
2019-11-15 05:49:39 v-update-sys-queue [Error 1]
2019-11-15 05:50:14 v-restart-service [Error 1]
2019-11-15 05:50:19 v-restart-service 'vesta' [Error 20]
2019-11-15 05:50:25 v-restart-service 'vesta.service' [Error 20]
help appreciated and thanks