What PSTN base are you using?  The older ones only allow 6 handsets to be registered, and perhaps yours has already exceed this number.  It's worth reading this: 

Thanks Guy, mine is a MK2. I should have included this information.

Im using the 6000mk 2 base and Becom 2 mk 2 phone and base.

Also using beoline mk 2

I got as far as entering date and time and lost the menu. it did not register with the other phones.

The Beoline 2 is only open for handset registration for 5 mins after powering it up.  Is that what you are trying?

Also, in the Beoline 2 manual it states:

If you want to register more handsets to a base, and one or more of these handsets are

BeoCom 6000 or BeoCom 2, the oldest handset model should be registered first. The menu options

will then be limited to match the options of the oldest handset registered.

So maybe remove the other handsets and start with the BC6000?

Thanks, I will try this .