I had to reboot my MacBook Pro (MacOS 11.4) in order to get Apache to work.
This is a real showstopper; I can't test my code without Apache. I upgraded to MAMP 6. 4 thinking things would be better.
The last three entries of apache_error.log
[Thu Jul 08 13:05:26.883132 2021] [authz_core:error] [pid 4526] [client ::1:61465] AH01630: client denied by server configuration: /Applications/MAMP/htdocs/.DS_Store, referer: http://localhost:8888/MAMP/?language=English
[Thu Jul 08 13:13:04.812757 2021] [:error] [pid 4529] [client ::1:61501] script '/Applications/MAMP/htdocs/tmp_phpInfo_AA39D1E0-4185-4550-BCA9-E6D16EDE086A-4034-0000158B727F2096_7.4.16.php' not found or unable to stat
[Thu Jul 08 13:13:22.237246 2021] [authz_core:error] [pid 4528] [client ::1:61648] AH01630: client denied by server configuration: /Applications/MAMP/htdocs/.DS_Store