Can I activate the Offers, Discounts and Pricing Management plugin again?

Can I activate the Offers, Discounts and Pricing Management plugin again?

Yes, you can always choose to reactivate the Offers, Discounts and Pricing Management plugin. However, there are 2 possible scenarios here.
Scenario 1: 
Your reactivation date is BEFORE the end of your current billing cycle. In this case, you just need to click the activate button on the Offers, Discounts and Pricing Management plugin tile (if you are coming from the Plugin screen) OR put a tick on the activation checkbox on the Offers, Discounts and Pricing Management plugin tile (if you are coming from the Manage Account section) to activate it.
Scenario 2: 
Your reactivation date is AFTER the end of your current billing cycle. In this case you will have to again subscribe to the plugin through the normal subscription process. 
Plugins in Tagrain are either Subscription Based or License Based. So the price that you pay for your plugins is based on the number of POS terminals that you have in your setup and the number of licences that you have acquired. 
There will be no change in your subscription amount in the current billing cycle if you are only deactivating the the Offers, Discounts and Pricing Management plugin AND not updating your Store / POS count.