I go to a group fitness gym, use to be a crossfit gym but they dropped the name/fees. Sounds like a crap gym if that was your experience. All people at my gym go through an introduction course, and the coaches are walking people through all the workouts, testing what you can do, and scaling it appropriately for your level. Today alone in class we had a 70 year old lady, and a girl in her 3rd trimester of pregnancy working out next to people who are very fit, all scaled to appropriate movements.

Or you messed up big time by not being honest, and they tried to help you as you stated, and you were dishonest with them on your capability, how you are feeling. We all start somewhere, and there is no shame in being the new person or out of shape.