Free EM Client 2 mail account restriction

Can the same email account be installed on 3 different machines using the same free EM Client version or does this fall under the 2 mail account restriction. Currently receiving sync errors with a 365 account. 

Thanks

For three machines you need three pro licenses.  No matter how many email accounts you have. The free version is only for one machine and two accounts.
Sync errors are a completely different matter and shouldn’t have anything to do with the license.