Follow the below mentioned steps to hide / unhide PayPal button from shopping cart page.

Step 1: Login to your Shopify store admin and click on the left menu: Apps.

Step 2: Now click on the Hider app as shown in the below screenshot.

Step 3: Below is the screenshot of how the Hider app's screen looks like. You can use the below highlighted Switch button to hide / unhide PayPal button.