Bluetooth LE connection drops immediately after connecting

Question

I'm building an application (runs on central device) in which I can scan, connect, pair, & reconnect in LE to a specific target device (peripheral device). My application is able to scan for Bluetooth LE devices and I have set the connection function. When I run my application, it scans until it find the target device and then it starts the connecting process.

On the target side (peripheral), I can see my central device was able to connect to it but the connection is dropped immediately. I think this is because it didn't find any compatible service (I think that just means there was no recognizable GATT attirubute/application/service?). I tried to connect to the same peripheral device through bluetoothctl and the connection drops immediately which makes me think something is missing from my target device (peripheral).

I'm wondering if I need to implement anything else before I try to connect to my peripheral device? Is it disconnecting because it didn't find any recognizable service on my central?

This is what I have from btmon on the peripheral side with another connection which was successful:

1. Connection request
2. Read remote supported features (understood remote as target device)
3. Turn off scan
4. Read remote extended features
5. Remote name request

Found this in the BTMON. "Attribute not found" possibly the issue?

> ACL Data RX: Handle 128 flags 0x02 dlen 11                                                       #23 [hci0] 16.564046
      ATT: Read By Group Type Request (0x10) len 6
        Handle range: 0x0001-0xffff
        Attribute group type: Primary Service (0x2800)
< ACL Data TX: Handle 128 flags 0x00 dlen 24                                                       #24 [hci0] 16.564325
      ATT: Read By Group Type Response (0x11) len 19
        Attribute data length: 6
        Attribute group list: 3 entries
        Handle range: 0x0001-0x0005
        UUID: Generic Access Profile (0x1800)
        Handle range: 0x0006-0x000f
        UUID: Generic Attribute Profile (0x1801)
        Handle range: 0x0010-0x0012
        UUID: Device Information (0x180a)
< ACL Data TX: Handle 128 flags 0x00 dlen 11                                                       #25 [hci0] 16.564349
      ATT: Read By Type Request (0x08) len 6
        Handle range: 0x0001-0xffff
        Attribute type: Unknown (0x2b3a)
> HCI Event: Number of Completed Packets (0x13) plen 5                                             #26 [hci0] 16.580038
        Num handles: 1
        Handle: 128
        Count: 1
> ACL Data RX: Handle 128 flags 0x02 dlen 11                                                       #27 [hci0] 16.596035
      ATT: Read By Group Type Request (0x10) len 6
        Handle range: 0x0013-0xffff
        Attribute group type: Primary Service (0x2800)
> HCI Event: Number of Completed Packets (0x13) plen 5                                             #28 [hci0] 16.596041
        Num handles: 1
        Handle: 128
        Count: 1
< ACL Data TX: Handle 128 flags 0x00 dlen 9                                                        #29 [hci0] 16.596267
      ATT: Error Response (0x01) len 4
        Read By Group Type Request (0x10)
        Handle: 0x0013
        Error: Attribute Not Found (0x0a)
> ACL Data RX: Handle 128 flags 0x02 dlen 9                                                        #30 [hci0] 16.620082
      ATT: Error Response (0x01) len 4
        Read By Type Request (0x08)
        Handle: 0x0001
        Error: Attribute Not Found (0x0a)