Missing Master page tab in Kentico 8 (after hotfixing or importing a website)

Please go to the Applications -> System -> Macros -> Signatures and Update macro signatures.

This is caused by the hash salt which is overwritten e.g. after the site import. It's also mentioned in the Documentation: https://docs.kentico.com/x/fQFb

Where you can find:

"The system uses signatures to ensure the security of macro expressions. The signatures are only valid in the environment of the application where the macros were originally saved.
To ensure that macros inside the data of imported sites or objects work correctly, you need to re-sign the macros using the System -> Macros -> Signatures interface. See Working with macro signatures for additional information."

This can also happen if you are using two projects which are configured to use the same database, e.g. one is the web application and one the is website. When you are connecting to the same database using different projects/project types, you will need to use the custom hash salt:
https://docs.kentico.com/x/lIQ8 especially take a look at the web.config key: CMSHashStringSalt