Assign User management for Sites

[Dale2]

I have a log file, I'm trying to reformat using sed/awk/grep but running into difficulties with the date format. The log looks like this:

1.2.3.4 - - [28/Mar/2019:11:43:58 +0000] "GET /e9bb2dddd28b/5.6.7.8/YL0000000000.rom HTTP/1.1" "-" "Yealink W52P 25.81.0.10 00:00:00:00:00:00" 404 - 1 5 0.146
I would like the output as so:

Yealink,1.2.3.4,28-03-2019 11:43:58
I have tried the following:

grep Yealink access.log | grep 404 | sed 's/\[//g' | awk '{print "Yealink,",$1,",",strftime("%Y-%m-%d %H:%M:%S", $4)}' | sed 's/, /,/g' | sed 's/ ,/,/g'
edit - removing [ before passing date string to strftime based on comments - but still not working as expected UPSers

However this returns a null date - so clearly I have the strftime syntax wrong:

Yealink,1.2.3.4,1970-01-01 01:00:00