Problem/solution fit needs to indentified & verified prior you can start looking for product/market fit or scaling. Here is a presentation that can help you on identifing the problem/solution fit.
Typically entrepreneurs feel pressure - both “internal” and external - to rush to scale. Many time even without understanding their problem/solution fit and how it differs between segments.
This results in not finding product/market fit or in inefficient and pre-mature scaling (read waste of money).
The aim of problem/solution fit process is to be able to identify the best opportunity to pursue further.