@graykat13 

There may be a potential issue with the firmware or the unit itself; however, it is advisable to first investigate the firmware.

Could you please provide us with the following information:

- Model number of your devices. You should see it at the bottom of your deco. See the image below for an example.
- Firmware version of your devices. You can locate this information in the Deco app by selecting More, followed by System.
- Hardware version of your devices. You should see it at the bottom of your deco. See the image below for an example.

That will help us proceed effectively. Additionally, could you confirm whether these units were recently purchased or if you have had them for some time? Are they all the same model, or do you have a mix of different models? Have you always had this issue? Or did it start after a firmware update? 

  @graykat13 

It appears there may be a firmware issue, as the system is designed to allow the addition of up to 10 Deco units within a single network. Currently, it seems that your network is recognizing 10 units, and when you attempt to add the final Deco, it is removing one of the existing units from the network.

I recommend that you submit a support ticket. I have included the necessary steps to do so below.

1. Email support at support.usa@tp-link.com.
2. Include the model number of your Deco router, as well as the hardware and firmware versions.
3. Describe the issues you are facing and send the email.
4. Within a few minutes, you will receive an automated response with a TKID number.
5. Upon receiving this email, please access the Deco web UI by entering "tplinkdeco.net" in your browser. Navigate to Advanced > System > System Log, select "ALL" in the log type, and save the file to your local computer. Then, reply to the email you just received, attach the log file, and kindly request that your ticket be escalated to a senior engineer for further assistance.