Cannot SUM the value of a field

I wonder if someone can help me with this SQL 2016 query.

I have two tables with following data

TblSalesRep This is the table holding the history of the territories that the sales rep looked after and the date range that they looked after it.

TerritoryId SalesRep FromDate ToDate
15 Anne 2020-01-01 2020-06-02
15 Dave 2020-06-03 2020-06-16
15 Anne 2020-06-17 2020-06-22
18 Anne 2020-06-23 2999-12-31

This is the table that holds the sales made by territory

tblSales
TerritoryId TransactionId TransactionDate ProductCode Amount
15 1 2020-04-15 Bags 50
15 1 2020-04-15 Bags 50
15 2 2020-06-02 Bag 25
15 3 2020-06-03 Shoes 60
15 4 2020-06-07 Shoes 10
15 5 2020-06-17 Bags 15
15 6 2020-06-18 Bags 25
15 7 2020-06-25 Coat 100
18 8 2020-06-27 Bags 20

I’m trying to produce a report that displays the SalesRep and the total sold between two dates for a given SalesRep.

For example, if I provided a SalesRep = ‘Anne’ and a date range of ‘1 Jun 2020’ to ‘30 Jun 2020’ I would expect a result back of :

SalesRep Sum
Anne 185

This is because it should exclude any business sold between 3 Jun 2020 – 16 Jun 2020 as the territory was looked after by Dave for a couple weeks and he sold that business between those dates.

I’ve tried using SUM function whilst joining to TblSalesRep but the figures are not what I’m expecting.

Could someone please assist.