@SaleebaD 

Try the following steps.

Step-by-Step Rebinding Process

1.     Log in to the Router: Connect to your TP-Link router and log in to its web-based management page (usually tplinkwifi.net or 192.168.0.1).
2.     Navigate to DDNS: Go to Advanced > Network > Dynamic DNS.
3.     Unbind Current Binding (If necessary): If the DDNS page shows a different or broken binding, click Logout or Unbind to release the current domain name.
4.     Wait for Release: If you get a "domain name already registered" error, you must log out of the TP-Link ID from the router and wait at least 15 minutes before trying again.
5.     Re-register/Re-bind:

•         Select TP-LINK as the service provider.
•         Click Register or enter your existing domain name (e.g., yourname.tplinkdns.com).
•         Click Save and Login to bind the domain to the new router configuration. 

Handling "Domain Name Already Registered"
If the domain is "stuck," follow these steps:

•     Log out of the TP-Link ID: Go to the Cloud/TP-Link ID section of the settings and log out, then log back in.
•     Use the Same Account: Ensure you are using the same TP-Link Cloud account that was originally used to register the domain name.
•     Alternative: If it still fails, you may need to register a new subdomain name or wait up to 24 hours for the old binding to expire. 

 Here's more on troubleshooting TP-Link DDNS.

  @SaleebaD 

I noticed that you're with the an old FW release for your VR300.

Get the latest FW release ( Archer VR300(EU)_V1.2_220407 ) from here and update it.

The try again the sane steps I've already mentioned.

If that still doesn't help then contact you local support for further assistance.