RE: Grand theft Auto 5 (Gta 5) Mission failed Montage

Have you tried the online heists? I remember laying down the materials for the heist and that took 2 hours to do. Then, the main heist was a matter of 15-20 minutes but we kept failing that particular heist for over 2 hours, it was getting useless to commence that heist. We came back the day after and completed it.