Hey, been having this issue for quiet some time too. I've recently changed my proxies from Instantproxies to Residential ones. This will hopefully resolve the problem. For now I'm letting my accounts rest for 2-3 days. Will update when that's done to see if it helped.
SO
1st Step - Change proxy (Instantproxies are good and cheap in my experience)
2nd Step - Let your account rest (I believe the follow block is timed, meaning you will have to wait 24-48h) P.s. I've kept hammering on it for a while, so the more you try the longer it gets
3rd Step - Start slowly and increase gradually 200-300 followings per day and add 30-40 per day
Ensure you acc is as active as it can be. I have this dude who's account I manage and he's posting 3-4 times per day. I run 700-800 likes daily, follow/unfollow 800 acc daily and comment 300 times daily. He's gained 2.2k Followers in one month.
And I also have a small business acc who is posting 2-3 per week. I get blocked after following / unfollowing 300 acc and liking 300 posts.
When blocks start, it's important to wait it out. If you keep hammering away it will only extend. I hope this helps...
If you have a bit more to invest, go with residential proxy tutorial made by Goso.io here
https://www.youtube.com/watch?v=vnJvZgwBc-4
I'm testing out this method myself but a lot of people vouch for this guy saying it solved all problems. 6$ per proxy but you can run up to 5 acc per proxy.
Hope this helps...