Ah, sorry, I misunderstood.

In 4.2 its controlled by a usergroup permission. By default thats turned off for guests.

(it was just the same in older versions, just controlled in options instead).

how do you turn it on for guests? like it was before with this mod?

Admin CP >> Usergroups

For Unregistered / Not Logged In, (COPPA) Users Awaiting Moderation, and Users Awaiting Email Confirmation:

General Permissions >> Can View the Visiting Members Display on Forum Home = Yes

And if you have Guest Tracking also enabled:

Guest Tracking Permissions >> Can View the Guests Visited Display = Yes
Guest Tracking Permissions >> Can View Guest Visits List = Yes

You should probably check these settings for your other usergroups as well.

Is there any way to have the number of guests show on 4.2.0 in the same section that the number of members show for the last 24 hours?

As in having it say this:

Total users that have visited in the last 24 hours: 169 members and XXX Guests

with the guests part added on?

Nope, this can only display visiting members, not guests.

Is there any similar mod that can display both members and guests active in past 24 hrs.?

Hello!

Try to install this on my new 4.2.0 forum, but I left the version says that is not compatible with vbulletin 4.2.0

Anyone know how I can fix?

Why would you want to install an addon that has been included in core vB?

See first post, right at the top, in bold blue:

Because I'm a noob xD

Thanks brother jejejejje xD