Access denied back end error when logging in

[Zedster]

I have been trying to upgrade for a week from 1.5.x to 1.6.x with nothing but problems and no real help from prestashop.

 

Here is a quick run down down.  Again! after finally getting everything backed up I used the 1-click (destroy your site) upgrade button.  The upgrade went ok according to the software.  But after further inspection of the web site it turned out that all combinations were not working on the front end. If you would go into the combinations area in the back end nothing would come up it would just keep loading like it could not find anything.  To me (I have very little understanding of databases) it just seemed like the link between presta and the database holding the combo info had been broken but no one can tell me how to relink this.  This is a problem that has been asked here 3 times with no answer in any of them.  So this seems to be a problem with software not something at we/I have done wrong.  

 

So after 2 days of no help, I was told by my boss to rollback to the previous version. When I do that I get this when I login.

For some reason this picture will not display larger.

 

Also all the statistics have quit working among a few other things.  

 

So now I finally get in touch with presta support, wow what an unreal fiasco that is. I am then told that they have no idea what is wrong but if I can rollback the site to when it worked they will fix it.  By fix it, they will move the entire site to their cloud run the upgrade and get it working and then return the site in working order.  But as I have said the site will not properly after the upgrade rollback.  So they say sorry we can't help. So today I try restoring the manual backup I took and the backup that my web host takes. Both exhibit the exact same problem, access denied upon login. At about this time, as i think that I should have the site up and running at least with the old version, I check the support ticket that Presta support sent me for the upgrade fix. To my wonderful surprise I find out that they want 600 euro to fix the problem with their software upgrade. I am told that this is good deal and I should be be happy by their support people. I strongly beg to differ.  I would find that understandable if I had done something beside exactly what is outlined on the site for upgrading but I did not.  It should just say do not attempt upgrading from 1.5 to 1.6 unless you can afford to have us fix it when it does not work. That would have stopped me in a second. 

 

So the situation right now is I have restored the site with a copy that I am 100% sure that it worked before this all started. But I am still getting the above page when I log in.  I am new on the job and now I am proved to be slightly incompetent. So on top of it all I have probably lost my job because of this but hey that's not your problem, is it presta

 

Can anyone help?

 

Sickened

 

UPDATE: Upon restoring a backup of the php DB my host had I have fixed the access denied error but now the site is completely inaccessible with an error 500. And this is the server side error:Premature end of script headers: index.php  This error could be about 20 different things from what I can find.  So now I have bqack end and no front end at all.

Edited May 17, 2016 by Zedster (see edit history)