WHY CAN'T I AUTOMATE A WORKSTATION?

In order to automate a workstation you must have;

I. the required level of the Beach Bum

II. the required amount of Cash

To collect the required amount of Cash is easy. You just need to do some grinding for a while.

To get the required level of Beach Bums for Automation you need to upgrade them. You can collect Beach Bum cards in the game in several ways;

Complete chapter goals,
Reach workstation buyers-level milestone,
Look for Card Offers in the Store,
Open Free, Rare, or Epic Suitcases
Use Gems to upgrade your Beach Bums

Automate your workstation by upgrading Beach Bum Cards to the required level in exchange for Gems.

Tap on the red automation button. The red colour indicates that you do not have the required level of Beach Bum card.

You will be greeted with the Automate Popup which will provide you with information about (1) the level the specific Beach Bum has to be in order to automate the Workstation & (2) the Cash amount you need to spend in order to execute the automation process (in this case we have the necessary amount of Cash). As you see the level progression bar is red, however, go ahead and tap on the ‘Upgrade’ button.

You will now be met with the ‘Upgrade Confirmation' button, where you can purchase the remaining replicate cards required for the upgrade (highlighted by the yellow square) in exchange for Gems. Tap on the green ‘buy’ button.

Returning to the main game screen you now find that the ‘Automate Workstation’ button is now green. Tap on it to automate it.

Now you find the ‘Upgrade’ button has changed into the ‘Automate’ button. Tap on it to proceed.

Now you will find that the ‘Collect Cash’ button has changed into an icon indicating that the station is automated and provides the period of time it takes for the profit to be cycled into your inventory (highlighted by the yellow square in the below image).