Visit chrome://extensions in your browser. Search for "Turking Guru" in the search box. In the information card for the Turking Guru extension, disable the extension using the toggle button in bottom right corner of the information card. Now enable the extension using the same toggle button clicked in the third step. This should restart the extension.

Click the logo of the extension in the same row as the address bar. A dialog box will appear showing your Turk Guru ID.

You can cancel the subscription from the customer portal. To access the customer portal, you need to activate the extension pop-up by pressing Alt+P on any mturk tab while logged in. You can also click the puzzle icon in the same row as the address bar, followed by clicking the logo of the extension in the menu that appears.