Like a good boy, I am testing locally first....

1) I note that the installer is still not aware of /local/configure.php so that forces the needless movement of configures around to make it happy.

2) So with /local/configure hidden and copied to the default location, the installer is telling me
An existing configure.php file was found. However your database seems to be current.
So I get no upgrade option offered, only a clean install.

In my admin, it states:
New Version Available: v1.5.5b :: Bugfixes for v155/v155a with mobile-friendly template

(You are presently using: v1.5.5a)
But on looking in table project_version_history I find these entries:
1 Zen-Cart Main 1 3.8 Fresh Installation 2008-11-11 09:47:34
2 Zen-Cart Database 1 3.8 Fresh Installation 2008-11-11 09:47:34
3 Zen-Cart Main 1 3.8 Fresh Installation 2008-11-11 09:47:34
4 Zen-Cart Database 1 3.8 Fresh Installation 2008-11-11 09:47:34
5 Zen-Cart Main 1 3.9a Version Update 1.3.8->1.3.9a 2010-04-23 16:49:58
6 Zen-Cart Database 1 3.9a Version Update 1.3.8->1.3.9a 2010-04-23 16:49:58
7 Zen-Cart Main 1 5.0 Version Update 1.3.9->1.5.0 2012-01-24 09:46:26
8 Zen-Cart Database 1 5.0 Version Update 1.3.9->1.5.0 2012-01-24 09:46:26
9 Zen-Cart Main 1 5.1 Version Update 1.5.0->1.5.1 2012-09-28 14:57:57
10 Zen-Cart Database 1 5.1 Version Update 1.5.0->1.5.1 2012-09-28 14:57:57
11 Zen-Cart Main 1 5.2 Version Update 1.5.1->1.5.2 2014-08-11 10:28:52
12 Zen-Cart Database 1 5.2 Version Update 1.5.1->1.5.2 2014-08-11 10:28:52
13 Zen-Cart Main 1 5.3 Version Update 1.5.2->1.5.3 2014-08-11 10:28:52
14 Zen-Cart Database 1 5.3 Version Update 1.5.2->1.5.3 2014-08-11 10:28:52
15 Zen-Cart Main 1 5.4 Version Update 1.5.3->1.5.4 2015-01-09 14:33:24
16 Zen-Cart Database 1 5.4 Version Update 1.5.3->1.5.4 2015-01-09 14:33:24

No mention of the 155 upgrade.

Now what?