Prints fail to adhere to build plate I have been using an Anycubic i3 Mega for about a month now and it worked fine. But when I designed a simple model in Fusion 360 and sliced it with Cura it started to have issues sticking to the bed. I thought the problem was the model so I tried to print a Benchy, but the same problem occurred. I readjusted the bed but it's still not working. I'm not sure how I can trouble shoot this.
The proper answer could be not related to Fusion, as you already noticed.
I suppose the issue is that the Ultrabase surface (or any other glass surface you have installed) was not cleaned during the first month? So it should be cleaned from grease and possibly dust. The general cleaning method is to use isopropyl alcohol (IPA) from time to time (btw. I am curious if it is advised in a printer's manual). If it does not fully help, I suppose using a dish soap with hot water prior to IPA is good step. Though I do not own this bed, so could not be 100 % sure of impact. (Definitely do not use any extra adhesion helpers for Ultrabed, because it has some specific microstructure which will get stuffed.)
You could want review other threads like this How to get Sunlu PLA to adhere to the printing bed? to get other hints and supplement your checklist. One thing to check first (and regularly) is proper bed levelling at current moment - and compare to initial layer settings in Cura (thickness, width, flow percentage).