Hi thingsarentworking,
We appreciate you reaching out to us.
We’d like to gather additional details that may help us be in a better position to assist you.
Would you please tell us more about your set up?
You mentioned that it only works if you "hold it up." Does it mean that the monitor only works if the cables are in a certain angle?
Have you tried a different set of cables?
In the meantime, let's try the steps below if your MacBook Pro is not able to detect a connected display.
- "On your Mac, choose Apple menu > System Settings, then click Displays in the sidebar. (You may need to scroll down.)
- Press and hold the Option key, then click the Detect Displays button on the right."
You can use the article below as a reference.
Use one or more external displays with your Mac - Apple Support
It may also help in isolating the issue if you can check if the issue persists on a newly created user account. For this test, you'll want to set up an Administrator account as detailed below:
"Add a user
- On your Mac, choose Apple menu
> System Settings, then click Users & Groups
in the sidebar. (You may need to scroll down.) - Click the Add Account button below the list of users on the right (you may be asked to enter your password.)
- Click the New Account pop-up menu, then choose a type of user.
- Administrator: An administrator can add and manage other users, install apps, and change settings. The new user you create when you first set up your Mac is an administrator. Your Mac can have multiple administrators. You can create new ones, and convert standard users to administrators. Don’t set up automatic login for an administrator. If you do, someone could simply restart your Mac and gain access with administrator privileges. To keep your Mac secure, don’t share administrator names and passwords.
- Standard: Standard users are set up by an administrator. Standard users can install apps and change their own settings, but can’t add other users or change other users’ settings.
- Sharing Only: Sharing-only users can access shared files remotely, but can’t log in to the computer or change settings. To give the user permission to access your shared files or screen, you may need to change options in File Sharing, Screen Sharing, or Remote Management settings. See Set up file sharing and Share the screen of another Mac.
- For more information about the options for each type of user, click the Help button in the lower-left corner of the dialog.
- Enter a full name for the new user. An account name is generated automatically. To use a different account name, enter it now—you can’t change it later.
- Enter a password for the user, then enter it again to verify. Enter a password hint to help the user remember their password.
- Click Create User."
You can use the article below as a reference.
Add a user or group on Mac
Take care!