Welcome, developer!
As you may have seen, we are moving to utilising a minimum fee per byte at block 2,200,000
. For more information on the reasons behind this decision, please check out this article from the core team: https://blog.turtlecoin.lol/archives/the-turtlecoin-journey-2-years-and-counting/
If you have an application which sends transactions on the TurtleCoin network, you will likely have to update your code to work correctly with fee per byte.