GST registration: separate registrations even working through sales force

can someone enlighten me in the following case:

an assessee is into stem cell banking business. Its whole process is centralised in a state except the sales force is located in various states. it doesn't have a fixed place of business in those states. the sales force meet up the clients and provide the kits required for cord storage etc. they bill for registration and do other formalities like filling form, etc.

question:
does the assessee needs registration in all the states where it has sales force working for it?