Let's keep this contructive please. :)

If you can post your output_log.txt (called player.log on Mac and Linux) from after trying to load your save, I'd be happy to take a look at it.Here's where to find the log depending on your operating system. To easily find the local files for the game, right click your game in the Steam library, select Properties, go to the Local Files tab and select Browse local files.

Windows
\SteamApps\common\Cities_Skylines\Cities_Data\output_log.txt

Mac OS X
Users//Library/Logs/Unity/Player.log

Linux
~/.config/unity3d/Colossal Order/Cities: Skylines/Player.log

As we can't attach files here on Steam, you will need to upload the file somewhere else. Here's a few sites you can upload it to, which do not require you to sign up first:https://uploadfiles.io/ - free, no sign-up, can handle large log files
https://paste.ee/ - fast, no sign-up required (some log files will be too large for it though)
https://zerobin.net/ - bit clunky, but can handle huge files, no sign-up required