NBU 10 about Licensing subscription type

good question
What demo license does is to shutdown netbackup services. No backups or restores are possible.
And essentially subscription is a demo license with bigger expiration date.

Probably a netbackup presales will answer that question

to add to what stefansM mentioned , which works for demo (Evalution) license.

"If you purchased perpetual license, it cannot expire. 
For perpetual license, maintenance expires, meaning you cannot download product updates or log Support call with Veritas. 

If you have Subscription license that expires, backups will stop, restores will be allowed."
quote from Marianne