Unfortunately, we've been scammed again on Appsumo.
This opinion is also confirmed by the low rating on Trustpilot:
https://www.trustpilot.com/review/zernio.com

The developer only sold an early version of the product, and then asked for additional fees for each additional feature, ultimately resulting in a monthly fee, which is expensive.

Two new add-ons have been added to the SumoLing panel:
◾Analytics (access to the analytical panel and API endpoints) – $150/month
◾Inbox (manage comments and direct messages across all platforms) – $150/month

Interestingly, the developer has changed his mind for regular users, but not for those who purchased through Appsumo, and has simplified the pricing.

(…)
Plus two things worth highlighting outside of product:
🔸 Pricing is now pay-per-account

We simplified pricing completely: no plans, no add-ons, no feature gates. First 2 accounts free, then $6/account (3–10), $3 (11–100), $1 (101–2,000). Every feature included. Price drops as you scale.
(…)

But that doesn't apply to you.

I don't recommend Zernio.com, because you never know what awaits you in the future, what new surprises await you.