If you encounter this error Script function __SW_GENERAL__OpenInSidebar_0 could not be found it likely means you're attemping to use SyncWith in a Google sheet where it hasn't been installed yet. This can happen if you install SyncWith in a Google sheet, and use it there, and then make a copy of the Google Sheet.
The solution is to install SyncWith on that new Google sheet:
If you've used SyncWith before on other sheets (with your current Google account) then simply use the menu in Google sheets:
Extensions->SyncWith->Get startedand that will install SyncWith on this google sheetIf you haven't used SyncWith before on any Google sheets (with your current Google account) then you'd need to install it, you can do that using the menu in Google Sheets:
Extensions->Add-ons->Get add-ons, and search forSyncWith, or install it from this link