FIX PHP website install & windows desktop app (server-side & client-side)

I have outdated php website (circa 2011) that is an online data backup system. Software is 2 part...server-side(website) and client side(desktop app) How it works: -end user selects a storage plan on website (paid or free) -user then downloads the windows desktop app (from link on website) which allows them to then sync files from their local pc, and send to the storage server (just as dropbox,carbonite,etc etc.) right from desktop Problem #1: (server-side) Well, the website worked a few years back, but when i tried to install few days ago, it doesnt even display the web installer so i cant continue installation to server. It gives 'server config' error. I know the code is old, so maybe just simple fix to get it to display or fix server. Problem #2: (client-side) This may be the trickiest part. the desktop application is written in .NET but very old (1.0 or 1.1 i believe). the app opens on desktop and you can configure and navigate everything, however, when you click to sync files, this is where the error comes in. Gives message stating that i must be signed in at the parent site in order to sync files...which i always am , so im just guessing app is way too old to work with the backup server. What i need: -i need the php website error fixed (sure its small fix) AND - i need someone to either re-write the functioning of this desktop app (maybe reverse engineer if possible) or write one to work with the site (after its fixed of course) I do not wish to pay hundreds of dollars to have one rewritten , and i also do NOT have the source code for windows .Net app, so ,however any experienced dev out there can help me, please discuss. *i have attached screenshots of the desktop app so u get idea of its functioning and layout.