Did you make sure the GM campaign folder was named the same as it was originally?
The campaign needs to be in the '..\Documents\Larian Studios\Divinity Original Sin 2 Definitive Edition\GMCampaigns' folder, with a name of the form GMName_1e35ce38-0f94-4ce7-97d1-febb116f0252'. You can get the UUID (letter and number section of the folder name) and confirm the campaign name (first part of the folder name) in the meta.lsf file in the root of the extracted folder, near the end. The last line (depending on window size) of that file would look something like below, so by comparison, you should be able to spot the UUID and campaign name (underlined here) that make up the folder name.
AGM_Area_Beach_Generic_A_d0505f3a-1dc1-2e5b-81f3-debadecb14df =  £¸4aà ð § ÿÿÿÿf4625c77-2716-44ad-a249-56b9f6b7d8f0 › ð(1e35ce38-0f94-4ce7-97d1-febb116f0252 GMName x 59¥
In the GMName_UUID folder in the Documents folder, the contents of the gmactivecampaignsession folder go into the root of that folder, as does the levelcache folder. The globals.lsf, top level meta.lsf and screenshot png file are only required in the save file, not the Documents folder for the campaign.
