Are you 100.00% sure you're looking at the correct lead and not one with a duplicate email address?
Thanks I really appreciate your help. Yes, I am 100% sure I can see the activities in the activity log for sales insight but not in the score view
So with no filters, do you not see the IMs either? Are there are other contextual activities shown but not IMs from the same time?
This is extraordinarily strange if so and I would open a Support case. But would indubitably triple-check that I was looking at the right lead.