In this case build one failing format from the format tab in miktex settings, copy the error message and ask for help.In quite a number of multiuser installation the on-the-fly installation created user map-files.Miktex has an offline database which contains informations about available packages, their content and how to install them.
When new packages are added to the online repositories, or if for some reason packages are rearranged or renamed the offline database on your PC is no longer up-to-date and you should "synchronize" (menu repositories in the package manager).
If you have multiuser installation synchronize in both package managers (admin user).
To install a basic Te X/La Te X system, download and run this installer.
Mi KTe X has the ability to install needed packages automatically (on-the-fly), i.e., this installer is suitable for computers connected to the Internet.
User formats (created with the button in the user version of miktex settings) wins over admin formats.