Was that a large account and which niche?
It may depend on reason your acc got flagged for.
Since IG recently started cleaning up fake follows/likes, your acc could've been in their hitlist. Also follows from another ip increases chance of getting their shits done fast.It's a 11,5 k followers old account (5-6 years old) in travel/fashion niche. Reasons could be: massive use of bot (not recently, about 6-7 months ago), purchase of fake followers and likes, actions blocked because of bad wifi connection (during a trip the account connected to a wifi and, after making a follow action, Instagram said "action blocked for violating terms blah blah..") or a report from competitors (i'm sure this happened). What are you thoughts?