Play Activity Not Updating
Basically, your play time is only stored LOCALLY. If you have a Nintendo account linked, then your Switch occasionally updates the online profile with your playtime. If the playtime’s greater than before, it will update on your profile. If not, it won’t update, and it won’t add to your existing playtime. It’s why getting a new Switch/formatting your existing one basically freezes the time.
Here’s an example:
Switch 1 tells Nintendo that you have 300 hours in a game. The profile reflects this. You play on Switch 2 for 100 hours in a game. 100 hours is less than 300, and will not update, nor add to the existing playtime. After playing on Switch 2, you surpass 300 hours, getting 500. 500 is more than 300, and thus updates on the profile. Switch 1 will show that you have 500 hours. You decide to play on Switch 1 for 100 more hours, with a total of 400 hours on it. 400 is less than 500, and will not update or add to the existing playtime.
Without a modded Switch, the only real way to track your playtime is to get a stopwatch and record how long you play and write it down. Or if you have one, use a homebrew app called NX Activity Log, which looks at the local playtimes instead of the Nintendo playtimes. This way, you can look at the locally saved playtimes and add them up.
I agree, it’s stupid, but it’s been multiple years of people reporting it and Nintendo hasn’t done anything, so I don’t know if Nintendo ever WILL do something, since when have they ever listened to us in the past?