bluetooth l2cap connect response 0x04

I have a question about below two devices connect classic BT L2cap profile,
device 1: iphone xs max IOS 15.3.1
device 2: BT 5.1 module
I need to do SDP service search, so l2cap connect is necessary.
when I use my BT module to send a l2cap request command to iphone, it sometimes get response with 0x04(no resources available).
But this issue wouldn't happen on android phone.
Can anyone teach me why iphone response 0x04, and hot to fix it?
Thanks a lot.
I got the btsnoop log on attaached image.

bluetooth l2cap connect response 0x04
 
 
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