Yes. Pokemon Go is down for 7 hours on Monday, June 1, 2020.
Pokemon Go creator Niantic has given this reason for you not being able to play the game today. To quote: “Pokémon GO will be experiencing global downtime for seven hours on Monday, June 1, 2020. From around 11:00 a.m. to 6:00 p.m. PDT (GMT +7), the game will be undergoing server maintenance and will be inaccessible to all Trainers. We apologize in advance for any inconvenience that this might cause.”
Here is a Pokemon Go Downtime Counter for you to check how many of the seven hours is left before the Pokemon Go server status changes from offline to online again.
Sweet Pokemon Go dreams! See you again tomorrow to try and catch ’em all! 🙂