Octalink alivio crankset problem

I’m having trouble installing a new crankset. My existing bb is octalink. It’s ok so I’ve left it in place. So I’ve bought shimano octalink crankset to replace the old worn out rings and cranks. The new crankset looks exactly same as the old in terms of compatibility. But no matter how I grease or try to carefully tease the crank onto the spindle (will a mallet or some man force), it will only go on about half the way. Thus I can’t set up my front derailleur properly. Any ideas?