How to remove ACL from a directory and back to usual access control?

Our problem was resolved by using:

setfacl -bn foobar

The point was we also had to remove the aclMask from the directory with an option -n... The man page of setfacl says as follows:

 -n      Do not recalculate the permissions associated with the ACL mask
         entry.  This option is not applicable to NFSv4 ACLs.

We're not sure why this option worked, but it did...

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In case you get d????????? permission after the above solution, try chmod -R a+rX as two commented below.

Odd... cannot reproduce:

ls -l | grep foobar
drwxr-xr-x+ 2 maulinglawns maulinglawns 4096 jan 24 14:25 foobar

setfacl -b foobar/
ls -l | grep foobar
drwxr-xr-x 2 maulinglawns maulinglawns 4096 jan 24 14:25 foobar

Unfortunately I don't have access to BSD to test right now.

System info:

Distributor ID: Debian
Description:    Debian GNU/Linux 8.7 (jessie)
Release:    8.7
Codename:   jessie