Goldie activity sync relies on scheduled Apex jobs as well as a properly configured Email Service handler in your Salesforce org . Both have a "context user" which is usually the sys admin that installed the Goldie managed package. It is vital for Goldie activity sync that this context user is not deactivated.
This is why if you try to deactivate the context user, a trigger on the user object will throw an exception, preventing this user from being deactivated. In order to resolve this you have to switch the "context user" of the email service and the scheduled Apex jobs.
In Salesforce go to Setup and find "Email Services" via quick find.
In the list of Email Services click on Goldie_Activity_Sync.
In the page Email Service: Goldie_Activity_Sync find the section "Email Addresses" and click the Edit link on the first (and only) list item (not the Edit button at the top).
In the edit page to Email Service Address find the field Context User and select a new user with Modify All Data permissions.
Click Save
In Salesforce go to Setup and find "Scheduled Jobs" via quick find.
In the list of scheduled jobs delete all jobs that start with "[DON'T DELETE!]: Goldie's...".
Once deleted re-create the scheduled jobs but under your own user:
In Salesforce open the developer console
In the developer console click Debug > Open Execute Anonymous Window (or type Ctrl + E in Windows or type ⌘ + E on MacOs)
In the execute anonymous window paste these three lines of code
AbSf.AbSfScanner.scheduleEmailAndRequestSyncScan();
AbSf.AbSfScanner.scheduleReplyAndCancelSyncScan();
AbSf.AbSfScanner.scheduleDailyScan(0);
Click the button Execute.
Go back the the "Scheduled Jobs" page as described in #1 and check if the scheduled Apex jobs have been recreated.
After you have switched the context users you can now deactivate the previous context user as originally intended.