No water in salt container

I have a John Lewis dishwasher model number JLDWS1202 which has been causing us problems for months now. The initial fault was a lack of heat and not drying which, after changing the heater relay and UTC to no avail, turned out to be due to a scaled up heater. We are now on our third heater but there is clearly a problem with the water softener – it’s set to the published water hardness in our area. I took out the IWMS and resin/salt unit last night to give them a good clean out. The resin/salt unit seemed ok after clearing out the salt ‘sludge’. I also checked the solenoid valve and it worked ok. There was loads of gunk in the IWMS most of which I managed to clear but not all of it. Put it all back together and ran a cycle but the salt container is not filling with water. I assume there’s a blockage but not sure if it’s in the IWMS or somewhere in the resin/salt unit. Does the salt container get filled via the IWMS or is it by backflow through the regeneration valve? Anything else I should be checking?

Doh! Just re-read the manual and spotted that the salt container has to be refilled with water manually on first cycle!