Hi,
At the end of the 60 day time period forwarding will stop or be reduced to 1Mbps unless a new (non-used license on that particular instance) is installed either before or after the expiration.
The other way around this is to delete the instance and then re-create it from scratch and the 60-day license may work again as it is countdown license from the first/initial boot of the instance. Basically delete everything and start again from scatch.
In case if that work around doesn't aid you, you perhaps should reach out to your SE (Sales Engineer) or Account teams to renew license. Reach out customer care for demo license is anothe option but i guess they may not entertain much as demo license period expries that are bound to customer account id.