Pricing Strategy assignment is suddenly not working for few customers

Summary:

We have all the pricing setups defined - Customer Profile Class, Pricing Segment , Pricing List , Pricing Strategy and Strategy assignment.

Price List and Pricing strategy defined for each Customer with their names.Pricing strategy assignment was done based on the Customer.

This setup was working fine till last week but suddenly pricing strategy is defaulted for few customers from last week and there is no setup change from ourside.

It works for few customers and doesn't work for many customers? How to fix this issue?

Content (please ensure you mask any confidential information):

Order Management Pricing

Version (include the version you are using, if applicable):