What do you mean by 'not allowing'?
Can you create a new profile, start a new game and save/load?
Try browsing to the '..\Documents\Larian Studios\Divinity Original Sin Enhanced Edition\LevelCache' folder and delete the contents.
If applicable, disable Steam cloud support either globally (in the client click on the Steam menu and select Settings, and then Cloud) or just for this game (in the library right click Divinity: Original Sin Enhanced Edition and select Properties, then switch to the Updates tab and check the Steam Cloud section).
Alternately, exit out of the Steam client, and just start the game directly from the '..\SteamApps\common\Divinity Original Sin Enhanced Edition\Shipping\EoCApp.exe' executable when required.
Next, try browsing to the '..\Documents\Larian Studios' folder and rename the 'Divinity Original Sin Enhanced Edition' subfolder.
This folder contains the saved games, configuration files and a level cache folder. Deleting or renaming it will get the game to recreate it on startup; playing the game from a different Windows user account would effectively do the same thing. With Steam cloud support enabled, Steam would just download the cloud copy of your existing profile.
After that, start D:OS, create a new profile and (if you didn't already test in a new profile) see if you can start a new game and save/load. Exit and then copy a couple saves from the renamed folder into the newly created profile's savegames_patch folder. If that lets you load the saves, move the rest of the saves over.
If that doesn't help, delete the new My Documents D:OS EE folder and rename the original back again.