How do I show fields from tables based on previous month?

Question

I have two queries here and my results are supposed to be clients provided bids last month instead my queries showing all clients in Query 1 and Query 2 same it supposed to show supplier that are unpaid last not all suppliers as my query showing. Please help me!!
https://code.sololearn.com/c1Prpi9Th72B/?ref=app

Answer 1

I think in where cause should be datediff