Many times the QuickBooks update error 15106 occur due to the presence of the QuickBooks folder having the same name as the updated folder. So to solve this the folder should be renamed to solve this error.
1. The QuickBooks update folder should be renamed.
2. open File Explorer
3. Go to C:Program FilesIntuitQuickBooks(year)Components
4. Go to C:Program Files(x86)IntuitQuickbooks(year)Components for 64-bit users.
5. Rename the downloadqbXX folder by right-clicking on it.
6. Downloadqbxx. old is an example.