On Essential Grid 4 the premium add-ons need a yearly licence: ESG Commerce, ESG Facets, Portfolio, Related Posts and Team. The other add-ons are free. With a CodeCanyon or one-time licence, the premium add-ons and templates already installed on a site registered under Essential Grid 3 keep working; new premium downloads need a yearly licence. You get 50 % off the first year of a yearly licence, once per licence; the offer is open for six months from the 4.0 release. A CodeCanyon licence gets the offer once you import its purchase code into your account.
Without a licence, premium add-ons you have not installed yet show in Essential Grid but cannot be downloaded. The upgrade page has your steps.