In the list of commands a familiar can do. Sleep is listed,
however when I tell him to sleep, no sleeping allowed. Miny
log enclosed....

<start log>
fam

Your familiar can do the following:
north south east
west down up
look where release
kill murder flee
visible scan sleep
socials stand rest
wake who faeriefog
faeriefire
<100%hp 43%m 100%mv 8136tnl outdoor 7 PM> fam sleep
You tell your familiar to 'sleep'.
>> You are unable to sleep.

>In the list of commands a familiar can do. Sleep is listed,
>however when I tell him to sleep, no sleeping allowed. Miny
>log enclosed....

This is by design. Sleep is a valid command for your familiar, however it is unable to because of it's immunity to sleep.

So long, and thanks for all the fish!