How to get Sunlu PLA to adhere to the printing bed?
Level the bed
Make sure that the bed is level. The nozzle must be equally high over heated surface, otherwise only part of the print will have chance to be smeared and adhere properly.
Clean thoroughly
First thing I do when I notice that increasing bed temperature does not work anymore, is washing the glass with soap or detergent. Some advice to use also isopropyl alcohol. My impression is that the main mistake is to use alcohol to wipe the glass instead of dismounting and thoroughly cleaning the glass from any grease. This is a bit more work, and for me works great.
Applying alcohol, brake cleaner or similar no-trace solvent could enhance the effect (as suggested by FarO).
Reduce the air flow
Disable fan for the first layer (or even more layers above).
Isolate the printer from environment - e.g. buy or build enclosure. Remove any drafts. Ensure that ambient temperature is not cooling prints down too fast (for example printing in garage or shed may fail until the space is heated).
Use kapton tape
You may like the idea to put kapton tape on the surface (only glass?). Wide kapton roll would be needed to cover big area at once, to cover the whole glass with good quality and in reasonable time. Created surface should be as ideal as possible, because any bubbles will cause later trouble, it is not easy but doable. The outcome is great. Any accidents with hotend should be avoided, and prints removed with some care, to remain tape undamaged as long as possible.
(I use 50 mm tape. And I save this surface for printing ABS, and only occasionally for PLA, because it sticks so well that I had problem to remove prints saving the surface, even after cooling down.)
Apply adhesive
You can use adhesives like hairspray, glue stick or even better a dedicated adhesion spray. It is suggested especially for larger parts, which tend to wrap without this kind of adhesive aid. There is no one good solution. You may want to experiment, starting from cheap and widely accepted to commercial and wildly advertised products, with regards to your local market. Look for example links at the bottom.
Expand line settings for initial layer
Make sure that amount of extruded material is correct. This mean proper calibration regarding settings like: steps/mm for E axis, flow rate. Small difference in amount of extruded filament will reduce the quality of the rest of the print. Bigger differences may ruin print at the initial layer, and for sure will spoil the rest.
Use slicer settings to increase line width for first layer. Values of 120-140% are standard settings for improving adhesion.
Slightly increasing height of initial layer may also help to overcome bed surface
roughness or slight leveling errors.
Decrease speed to 20 mm/s or less
Reduce printing speed for initial layer to 20 mm/s or even lower, and raise it carefully after trouble is really resolved. (In my opinion it is better to decrease speed to let plastic melt and stick, than to increase temperature.)
Modify temperature
The temperature of heated bed should be high enough to keep the initial layer of filament within glass transition zone. This usually means more than 60 °C for PLA (between 50 °C - 80 °C depending on contents). (I usually print at 70 °C, and raise to 80 °C when meet issues.)
Increasing the temperature of nozzle also may improve the adhesion. But it may also be temporary success, because of negative effects related to temperature differences, and for example cause wrapping - ruining especially wider prints. So decreasing the nozzle temperature is also an option to check, when wrapping is observed.
Experiment with more advanced techniques
If you are still failing, then try experiment following many advices around (contrary, but sometimes working). If the firs layer adhere to the bed, but problems appear later, then other advanced techniques may help - like slicing model with additional structures (brim or raft).
The best advice may depend on kind of heated bed, surface or environment. This checklist may be of some use: 3D Printer Bed Adhesion: All You Need To Know. Also there are many troubleshooting threads on the web, like this on Reddit: SUNLU PLA+ will not adhere to build surface, or; this on Thingiverse: SUNLO PLA+: does not stick..