If you can't import any management packs at all, no matter how you try then check the OperationsManager database for free space.
The SCOM in-product catalog site can go offline from time to time - have you been able to access it in the past?
In general I would suggest downloading and storing the management packs in a SCOM software library and then choosing import from disk - I note that you say that the import from disk also fails but does it work if you state not to go online to check
for dependant management packs?
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