There is a trouble shooting procedure in the lenco tab manual. But I would start with the power feed to the switch. ( wire on the ends from memory)

CBF
Whk

Fuse?

Technical guess is that it isn't an expensive trim tab issue, unlikely they both fail at once. More likely power supply, fuses switches, terminals.

Found the fuse and inspected. Fine. Replaced anyway.
No luck.

Checked connected at switches, all good.
Checked and control box, all seems fine.

Traced orange wire to isolating switch and all fine. The positive and negatives are connected and clean.

Im suspecting it's either a faulty switch or a bad connection somewhere between the helm and the actuators.

Will need to give it a good look on Monday

A good trick for troubeshooting is a light bulb attached to leads - hook one wire to battery - other follow power from battery through switch to trim tab - bulb will light bright if power - dim/out bad connection.  Can use a multimeter but 12V can be tricky sometimes due to impedance (bad connection) voltage drips - meter reads ok as doesnt draw any current - I have been caught out.  To test under load best.

Update:

I fixed it in the end. On the way out early on Sunday morning I noticed when I turned the Nav lights on the switch panel there was a light to indicate the power to them.

Yippie!