I am using the API to get analytics data display, For that first I am checking data and parameters in this ga-dev-tool. have checked both ways in ga-dev-tool.
When I try without pagepath its works properly and I get data of transactionsPerSession and transactionRevenue. But when I try with pagepath in the same way it's not working and giving 00 for all these 2 values.
https://ga-dev-tools.web.app/query-explorer/
https://ga-dev-tools.web.app/request-composer/
Here I have also attached images for result with query parameters :
If you want to get transection related data from API
Then You have to pass ga:landingPagePath
Instead of ga:pagePath in dimension Filter
Let me know if you still getting incorrect transactionsPerSession.