Cannot change to new order status

Hi,

I install the plugin “custom order status for woocommerce”. Everything was set up according to the instruction. The new custom order status “Ready to Ship” is shown up in order list table and order detailed page. Email notification was set up correctly. But in both the order listing page and order detailed page, I cannot change the status to “Ready to Ship” but it was changed to “pending to payment” ( paid status of the plugin was turnt ON.

Pls advise what is the problem.

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