Hi Keith!
There are two potential inter-related causes for this. In order for the NEXT and PREVIOUS arrows to work, the application must have the NEXT and PREVIOUS signature options defined (Select Action > Add / Modify Signature Options) AND the logged-in user must belong to a security group to which the NEXT and PREVIOUS options have been granted.
So, I would first check to be sure that NEXT and PREVIOUS are defined as signature options (if not, you can add them as they are standard and the application bean will know how to process the correlated events), and then ensure that the user(s) have the security grants.
Best wishes,
Jade