Zanussi washer/dryer Mod. Z716WT83BI Error code E73& no heat?

Hello
I have the Zanussi washer/dryer Mod. Z716WT83BI 914606600 01
I took the top off the machine to clear out the condenser of lint as shown to us by engineer last year when we had an issue of the dryer not drying clothes properly. It has been taking a lot longer than usual for clothes to dry on dryer mode.
The contents was some lint, not really clogged like April last year. On putting everything back together and powering up the machine It does not dry at all now or get hot. The wash side of things works ok. If you put it on a dry, it starts at the standard, 2 hrs 22 mins, it has buzzed a few times on starting the drying mode. After several minutes of adding water and spinning the time drops down to 40 minutes and then after a few more minutes down to around 11 minutes. There is no heat.
I have checked all wiring is ok.
On pushing and holding the play and auto dry shown to me by the engineer which I videoed last year we managed to get something showing E 73 although I’m not sure if this is related to the current issue. Any help or advice extremely appreciated. The machine is just under three years old.