API Modify a pool fails with error 1002

Issue when trying to modify a pool via API:

Hi, trying to modify a pool by running:

curl -X PUT “https://api.cloudflare.com/client/v4/user/load_balancers/pools/d7asdjgh675jehajhsdblabla
-H “X-Auth-Email: mymail”
-H “X-Auth-Key: mykey”
-H “Content-Type: application/json”
–data ‘{“name”:“1-server”,“enabled”:true,“origins”:[{“name”:“server1”,“address”:“www.mysite.com”,“enabled”:true}]}’

and I get a response:

“result”: null,
“success”: false,
“errors”: [
“code”: 1002,
“message”: “Probing from every data centre is not allowed with this subscription. Please choose regions to probe from.: validation failed”

Can anybody tell me where is the issue?
I have a free site account.