I agreed with @drakko but just know that Bambu cut off our retreat back to 1.3 and if you were counting on backreving pre 1.4. your screwed.
Having said that. You did not mention if you dried you filament first and cleaned the plate with dishwashing detergent and very hot water. Both of these would produce the exact same problem you described.
Another thing you can do before you clean your plate, try moving the print to a location on the plate that gets the least amount of use. See if you can get different results. If you do, that’s the smoking gun that your plate was contaminated.
BTW: I stopped using Bambu PETG because it’s not only 2X the cost of what I can get on Amazon and also inferior, but it required a lot of drying right out of the bag.
Also, have you performed a first layer test on your build plate? Until you have, you can’t really be certain that you don’t have contaminants on the build plate.
Here are two example photos where I deliberately smudged the plate with my finger print. I used the high temp plate because fingerprints readily show on the smooth black surface. On a textured PEI plate they are invisible. I then printed a first layer test and you can easily see how the material did not adhere.
Here is the same experiemnt with textured PEI.
Blank Plate. Looks clean, right?
First layer test. Not so clean after all.
