How to fix Unable to join party BO3?

I think you got the wrong game, it's actually Black Ops 3, and me and my friends are from Xbox

Apogolies you are right

About Black ops 3

These the solution that are recommended to follow to fix the issue with unable party join:

- Check for Black Ops 3 Updates

Make sure to turn on your Xbox One or Xbox Series X|S gaming console.

Press the Xbox button on your controller to open the menu.

Now, scroll down to the right > Select Settings.

Scroll down until you see Updates & downloads.

From the next page, select Keep my console up to date and Keep my games & games up to date to enable the checkbox.

- Try Forwarding Call of Duty Crossplay Port

Log into your Wi-Fi router’s admin dashboard via the browser.

Now, go to the Port Forwarding option > Type the Xbox IP address in the IP address bar.

You’ll find the Xbox IP address in the Xbox Network Settings menu.

Then input the TCP and UDP ports as follows.

TCP: 3074

UDP: 27014-27050

Finally, save the changes and restart your router.

- Try Disabling Crossplay

One of the important steps also to try disabling and enabling back the crossplay feature on your Call of Duty Black Ops III game to ensure there is no issue with the ‘Failed Fetching Crossplay Friends List’ error further. You can follow the steps below to do so:

Turn on your Xbox console > Navigate to General Settings.

Select Online safety and family.

Go to Privacy and Online Safety > Select Xbox Privacy.

Visit View Details and Customize.

Choose Communication and Multiplayer.

You’ll have to select Cross-network play > Just turn it OFF and wait for a minute.

Then Turn Crossplay On again and restart the game to check for the issue.

- Delete the Friend from the list and Retry

Launch the COD Black Ops III game.

Go to the Social menu of your Call of Duty: Black Ops III account.

Now, select the friends with whom you’re having crossplay issues.

Then choose the Profile and hit Delete.

Make sure to add the deleted friends again using their Activision account IDs.

Finally, reboot the game and check for the issue.

- Adjust Party Settings in COD Black Ops III

Launch the COD Black Ops III game > Go to Social.

Select Manage Party > Here you’ll have to set the party size to 18 friends or less.

You should also cross-check if the party is set to open/friends only.

Hi, I'm Miguel, community expert, I may not be an employee of Xbox, but I see you need some help, I'm Happy to help you.

You should ensure that everyone you want to party up with has crossplay enabled.

To enable crossplay:

Open Black Ops Cold War multiplayer

Go to Settings

Navigate to the Account tab

Enable or Disable Crossplay

Its the same with mine moderate in BO3 open on Xbox One but I have no problems joining party's chatting in game joining friends or matchmaking so it's probably just a visual bug.

While I didn't get an IP error, my party chat actually did start working after doing these steps...awesome.