The 2021 ACM Awards gave Dan + Shay, who won Duo of the Year during the show on Sunday night (April 18), plenty to celebrate; however, they also dealt with some technical difficulties during their performance.

As the duo sang their new song "Glad You Exist" from Nashville's Bluebird Cafe, an audio/video sync issue occurred, causing some fans on Twitter to wonder if the duo might be lip-syncing. Rather, Dan Smyers and Shay Mooney explained backstage in the virtual ACMs press room, an audio glitch that occurred during their performance, which was pre-taped in advance of the show, caused the problem.

"It's been a difficult time to put these awards show together during these crazy times, and a lot of us have had to pre-tape our performances, and that's what we did," Mooney explained. "We pre-taped it yesterday. We were super stoked about the performance."

The glitch, he continued, was the unfortunate result of how complicated it is to create the awards show, particularly since the ACMs air from multiple different venues across Nashville.

"It's just one of those things that happens, you know," Mooney added. "There's a lot of things going on. So it happened, we were bummed, and it is what it is. And they did a great job putting together a great show."

The 2021 ACM Awards air live on CBS and stream live on Paramount+. Sign up for the streaming service here.

See Pictures From the 2021 ACM Awards Red Carpet:

The best dressed on the 2021 ACM Awards red carpet brought color — lots of color — for an awards show that promises to be a celebration. Photos show stars like Carly Pearce, Kelsea Ballerini, Chris Young, Kane Brown and more wearing the hottest and often most expensive designer outfits, or suits they designed themselves, in the case of Jimmie Allen.

Check out a full gallery of country music's hottest stars on the ACM Awards red carpet. Who do you think is best dressed and worst dressed?

The 2021 ACM Awards took place at the Bluebird Cafe, Grand Ole Opry and Ryman Auditorium in Nashville on Sunday (April 18).