installer didn't add new field to customer table.

Updating from 1.5.6c, the new field for registration_ip was not added in the upgrade. I do see it in the present sql file but not as added since I did that update. This was on a website where 71 logs were created during the upgrade. Do I then assume this was due to the state of that website and not a bug in the upgrade? I have another upgrade from 1.5.6 coming up this week.

Typically this occurs because there's a date in the table that's in the old format.

https://docs.zen-cart.com/user/upgrading/date_standardization/

If the site uses the GDPR mod, note that several tables may have this issue - check carefully.

yeah, the GDPR was there. You had mentioned that before. Good. Next one will be easier!! Thanks.

Look very carefully at the logs created by the install process - they will tell you when things go wrong.

General suggestion would be to fix the identified issues back on the live site, again make a backup of the database and then perform the update/update test to correct any remaining issues.