Page 5 of your instruction book says:
"The FP715 Si is fitted with an installer service interval timer ... Setting instructions for this gas safety feature are only available to bona fide heating installers".
It's designed as a feature for landlords, to ensure that their tenants get their boilers serviced regularly. It limits the boiler operation until the service is done
Your 'engineer' should have reset the service timer when he did the service - get him back to do it, for free! If he doesn't know how, he's a cowboy. He needs to ask Danfoss for the instructions. If he objects, threaten him with your local Trading Standards office - he didn't do the job properly.
jaybee
November 2008