The 4LCD-A card, when programmed (Command 10), will need a Time Slot for each SLT assignment you add. If the LEN you want to program says "NONE" the LEN is OK to use. Before or after you assign the SLT #, and if you want to check if you do have Time Slots, do the following command: F70>LEN#>   It's the first four digits your concerned with. If you see (after the : mark) 00 01 the 01 means a time slot is available. If you were to assign the SLT to the LEN but no TS was available, the Command 10 programmming will of course be accepted, but when you go off-hook on the Single Line Telephone you would not get Dial-Tone, just Talk Battery.

Resetting the CP03 or CP00 card (which ever one you have) will automatically re-allocate the Time Slots. If you still don't have Time Slots available after the MP reset, that means a card (or cards) that use many TS's is programmed within that FP (CP01). Example - An 8RSTA card (register card) will need 8 time slots although that card physically occupies only one LT slot.

If you have more questions or trouble - repost you issue, I'll be looking for it.