Black Six

The version compatible with IPS 4.7.3 is currently pending approval.

I have corrected this for you. Seems to have been an issue with caching

You had an empty string on your conf_global that was causing this on the following constant. This was resolved by my colleague in the ticket to get your site online.
$_INFO['board_start']

You had a custom URL set in your storage method. This has now been corrected for you, and your site is back online

You will also need to update your IPB license  as the URL is changing.  You’ll need to do the license reset after the migration because the old URL cannot be accessible in order to apply the reset process.
Review your upload paths as that directory is most likely changing. 

You’re on the right path for conf_global and constants file.  I would setup your 301 in htaccess in your old location instead of other locations.  Make sure the new location gets an updated htaccess reflecting the correct change. (If you are using the API’s, you might need to correct it’s htaccess also.)
 

The order in which you do this should also be
Move the site files Update your conf_global.php and constants.php Make any changes to custom URLs you have set in file storage settings (if you are unsure, its unlikely you have any) Change your licensed URL (go to your client area, select your license, then 'change URL') Do your redirects Its important the redirects are done last, otherwise you will have problems changing the URL on your license

Please be advised I have moved this to a ticket for you for further investigation. You will receive a response via email for any further communication.

Can you update to 4.6? @newbie LAC

You can view the status of IPB 4.5 updates here - https://www.devfuse.com/forums/topic/12381-ipboard-45-update/