Thank you so much... It makes sense. I checked my versions. My windows is 6.25.1.9091 and Android is 10.37. It's just that it happened recently and I haven't updated the apps. I'll try to run the same versions.
After I create a checklist and sync, it displays on both PC and phone but when I update it on my phone, like checking a box and syncing it, the display on the PC changes. The check box turns into a bullet.