Answer: Yes it was
Step-by-step explanation:
An insurrection refers to an uprising against the government of a place usually by violent means and with those involved being armed.
Shay's rebellion saw people attack government establishments and properties in Massachusetts and then they attempted to attack a Federal government arms depot so they could take the weapons and continue the rebellion.
This fits the definition of an insurrection as the people were both armed and had risen up against the government.