Reasons for a PLA print not sticking to bed all the sudden?
There are 3 general factors about print adhesion you always have to keep in mind:


Have a sufficient surface for the print to stick. A pyramid printed on the tip can't print properly.
Check the leveling of your bed occasionally and relevel the bed. By removing prints, one can easily unlevel it over time without noticing it.
Clean your print bed from fingerprints and grease every so often. Fats are good separators between the print and the bed. Getting them off with Isopropyl alcohol or other solvents can restore print surfaces in an instant.


In this specific case, there are some hints that make the general things less of an issue though: Old sliced items print fine, newer not. This hints that you changed something in the print settings. Among the settings that are good for adhesion, check your old G-code for the following three:


Bed temperature. I use 60&nbsp;°C bed temperature for PLA and have good results on bed adhesion. Others print with 50&nbsp;°C. However, going too low can make the plastic not stick well anymore.
Extrusion temperature. When the plastic extrudes, it has to be molten enough to push out enough and cold enough to solidify within moments and stick to the surface of the bed. If it is too hot, it would be dragged along, if it's too cold it doesn't get to stick either. I use 190-200&nbsp;°C for PLA.
The first layer height might be different. I usually use 0.2&nbsp;mm for this setting, no matter what the actual layer height is, and get good adhesion and not too much trouble with tiny unevenness.
The reason might be a mechanical issue, in that the Z-endstops (in an Anycubic i3, there are two, hidden in the frame sides) might have bent, moved or misaligned over time. Check its positioning. If the mount is broken, there are replacement part designs.