Your problem seems to be one of bash string concatenation
The frist request ran and the second request made a call to <cursor_info> and of course <cursor_info> is not a valid URL so the host look up failed.
curl -H "Client-ID: $client_id" -H "Authorization: Bearer $token" "https://api.twitch.tv/helix/users/follows?to_id=$user_id&after=$cursor" | json_pp >> fl_list.txt
may work, I’ve not tested but matches my quick remind google
I did a quick google to remind myself of bash and referred to https://stackoverflow.com/questions/50613030/scripted-concatenation-of-strings-in-curl-command-payload