A computer system update should not have affected Manager. Before you do anything else, shut down and restart your computer and relaunch Manager. (Do not merely restart. Actually shut it down.) If no company is present when you open Manager, you have probably moved the application data to somewhere besides where Manager thinks it is. Click on About Manager to see where the program thinks data is. Read this Guide, which may help:
https://forum.manager.io/t/managing-contents-of-the-application-data-folder/8394
If you cannot remember where you put the data, search your disk to find the file 00000000000000000000000000000000.manager. Whatever folder that file is in probably holds the rest of your data, too.
What operating system are you using?