Tried this but problem still exists.

Initial clear produced receipt that says Initial clear ok

Try to connect, hangs on 'get status' and then 'register not ready' pops up.

I've tried three different connection cabels now, so suspect it isn't that.

Model is ER-5240, not 5240M if that makes any difference.

Any other suggestions?

where did you get the cable from that joins the till to the rs232 converter?
check that you are using the correct pinouts?

Just a update that the problem has been solved by purchasing the right type of cable. With little knowledge of serial cables, I bought an 'extension' cable from ebay which didn't work. Since bought a specialist sam4s cable which is configured differently, so I can now program the till.

Thanks to everyone for their pointers.

how did i guess?