If you're an Album Admin (parent member) registered for Premium, you should receive Monthly 1s Movies every month on or around the 10th of the following month.
Plus, if you're a first-time Premium subscriber, you'll also receive a bonus Monthly 1s Movie for the month prior to subscribing. That means if you subscribe to Premium for the first time in July 2020, you'll receive June's Monthly 1s Movie in addition to all 1s Movies thereafter. Don't worry, you'll still get Seasonal 1s Movies in addition to the monthly ones!
*For the first-time subscription bonus, if you subscribe after the 10th, you should receive your bonus 1s Movie shortly after subscribing. If you subscribe before the 10th, you'll receive your bonus 1s Movie on or around the 10th of the month. Please note that the subscription bonus only applies for albums that have not previously been registered for Premium.