As mentioned by many users, are you increasing this VIA a local script, or a script? You seem to be extremely unresponsive, and have provided little to no context at all. How are we supposed to help you without crucial information?
This also goes to the many users who posted on this post, that you should not be repeating the same thing(s) other users are, and maybe quoting what they are saying would be more useful.
In your case, hireimgeorge, if you are using a local script, this needs to change immediately.
As many people have said, if you are changing the player’s strength locally you need to have a RemoteEvent or Function to make sure the server value is switched as well.
The problem is that when a player gets more “strong” it will only change the value locally which means that they are the only ones that will be affected by it. If you need help with RemoteEvents, I recommend reading this.