Despite retaining Mateta, who is Palace’s top scorer with eight league goals this season, the Eagles paid a club record fee to sign striker Jorgen Strand Larsen from Wolves.
Palace were also on the verge of bringing in Everton winger Dwight McNeil until the deal fell through late on deadline day.
Glasner said he had “learned to accept situations” after Palace were also unsuccessful in finding a replacement for captain and centre-back Marc Guehi, who joined Manchester City earlier in the window.
“At the end of it, the club tried everything with huge offers and huge bids for a Marc Guehi replacement, but clubs said they don’t sell on deadline day,” Glasner said.
“Credit to the club that without getting any money for Mateta they still spent a big fee on Strand Larsen.
“On the other side, McNeil was the last one we thought we could finalise, but in the last minutes the terms of the deal changed again and the deal failed. I expected him and planned for him in the next day’s training.”
McNeil’s partner, Megan Sharpley, criticised Crystal Palace on social media for the way they handled the situation.
Everton boss David Moyes said the breakdown had “nothing to do” with his club and insists McNeil is “fine”.
“He’s in and he’s training as well, so Dwight’s OK,” Moyes said.
“We understand exactly where it went wrong, how it broke down. He knows everything about it and there’s no problems there.
“We had given permission for Dwight to go and have a medical and do all of the things required for it, so it was very hard to do much more than we have done.”