If you are not able to find the +Add Client button.
Ensure the user has correct permissions:
Log in to Tax.
Go to the Settings cog.
Click Users.
Click on the username, then click the Permissions tab.
The Create Client should be set to Allow.
Have the user log out and log back in to Tax.
If the button still does not display, try the following:
Close out of Tax and clear the Cache/ History from All time, then close the browser.
Open a new browser and log back into Access Tax.
If you are still not able to access the +Add client button, try a different browser.
Try Incognito or inPrivate browsing mode.
Log in using a different computer.
Temporarily disable any Anti-Virus software for testing purposes (re-enable to Anti-Virus after testing).