Activation error: Licence key activation limit reached. Deactivate an install first.

Activation error: Licence key activation limit reached. Deactivate an install first.

Hi,
We have aquired Event Manager Pro 1 Site license with a bunch of plugins. Activation code is the same for all. We copied plugins through ftp in wp's plugin folder(some zip's are actually too large to be able to install from dashboard directly).
Our issue is that from day 1 plugins can not be activated, we get "licence key activation limit reached" error, regardless what we do. I've managed to activate only 2 plugins:
- Sell Tickets
- Stripe Split
Rest of the plugins return this error message.
Please help. I've already opened a ticket for this 2 days ago but received no answer to it.