If you don't know your SteamID, you can simply just paste in your profile URL.
Click on your name in the upper-right corner of the Steam Desktop client, and select "View Profile".
Once you're on your profile page, just right click literally anywhere on the page and select "Copy Page URL".
If you know you have the right ID or URL, your profile might be set to private at some level.
To fix this, go to your profile and click the EDIT button on the upper right side, below your steam level:
Click "Privacy Settings" at the bottom of the left-side menu and make sure "My profile" and "Game details" are set to "Public"
If games appear to load, but no playtime is showing and the range inputs are disabled, you are probably hiding total playtime in your profile privacy settings.
Click "Privacy Settings" at the bottom of the left-side menu and make sure the "Always keep my total playtime private..." checkbox under "Game details" is NOT checked: