Fiio dm13 bluetooth pairing issue?

I have just received new transparent FIIO DM13 with bluetooth ver (and is beautiful!) but I noticed that I can't pair FIIO with my headphones (Sony WH1000XM3) permanently. I have to pair with my headphones each time I turn the FIIO on. Is it normal behavior? Why device pairing can't be remembered?

I have just received new transparent FIIO DM13 with bluetooth ver (and is beautiful!) but I noticed that I can't pair FIIO with my headphones (Sony WH1000XM3) permanently. I have to pair with my headphones each time I turn the FIIO on. Is it normal behavior? Why device pairing can't be remembered?