error/qtype combined/nosubquestiontypesinstalled

In order for the Combined question type to work, You need to have installed in your Moodle server two or more of the following four additional question types:

• Numeric (n.b. based on Variable numeric and not Numerical)
• Pattern match
• OU multiple response
• Select missing word

Please install two or more of these additional plugins from the Moodle plugins database and try again.