DIAGNOSIS This is almost always a setting in the MyQ app itself. There's a feature called "Open to" that lets you set a partial open position, and it's probably been accidentally activated.
FIX Open your MyQ app. 1) Tap on your garage door device. 2) Look for a setting called "Open To," "Vent Position," or "Partial Open." 3) You'll see a slider or a percentage. Slide it to 100% or select "Fully Open." 4) Save the setting. Now try opening the door with the app. It should go all the way up.
IF THAT DIDN'T WORK Check if you have any routines or scenes set up in the app (or linked via Alexa/Google). A routine might be programmed to only open the door to a specific position for, say, letting a pet out. Review and delete any such routines.
HEADS UP This "Open To" feature is useful for ventilating the garage without fully opening the door, but it's easy to bump into on the app screen. If you have kids using the app, they might have changed it without realizing.