You will need to increase your fame.
That is done by releasing better and better magazines, and by throwing successful parties.
And throwing successful parties gives you the contacts needed to produce better magazines.
I suggest the following:
Hire two of the best writers and photographers you can, and build maxed out business relationships with them, try to avoid drunks and the angry sort.
Then be sure to hire the best playmates you can, again avoiding the drunks and angry ones, and make sure than you have a girlfriend spot available when you have the photo shoot for them, or that you are prepared to get content from them quickly
(published playmates get a big bonus to their fame, so always try to get their photo shoot, and then the interview/essay/cover shot before they leave)
When hosting parties, keep a bunny on staff to entertain, and keep your staff and a playmate on the list, and focus on three celebrities who match something the public wants to see.
I spend my time making friends with a celeb while my staff make friends with the other two. If you get the celebs in the inner circle you can get them back easily for content, but each party can provide enough content for one issue of the magazine.
So successful party + successful magazines = greater fame > higher fame guests start saying yes.
You can pm me if you have more specific questions