why I can't put my macbook pro on sleep anymore?

Check your system's sleep settings: Make sure the sleep settings are set the way you want. To view sleep settings, choose Apple menu > System Preferences, then do one of the following: ... You can also deselect “Prevent computer from sleeping automatically when the display is off” in the Power Adapter pane.

This article might also be of help.

https://support.apple.com/guide/mac-help/if-your-mac-wont-go-to-or-stay-in-sleep-mchlp2995/mac

kim009 wrote:

why I can't put my MacBook pro to the sleep mode anymore?

To trouble shoot further you can:

—Try a SafeBoot https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen, does a 5 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc.

Login and test. Reboot as normal and test. Caches get rebuilt automatically.

In Safe mode third party system modifications and system accelerations are disabled, it removes malware, etc hampering smooth operation, however a reboot will put it back to normal mode.

This test will tell you if third party interference; extensions etc are not loaded in safe boot mode.

—Test issue in another user (or guest user) account https://support.apple.com/guide/mac-help/set-up-other-users-on-your-mac-mtusr001/mac

This will tell you if it a universal issue or isolated to your user/admin account. 

Uninstall all third party apps that are Cleaners/Optimizers/VPN/Anti-Virus