Looking at the logs i don't see anything related to sparkpost.
can you please empty the application log and then try to enable sparkpost once again so that it shows you the same error? then go to application logs and see what it's there.
P.S: removed the log file for privacy reasons
@Tiago Barbosa - And still sparkpost shows same error with a status 500 ?
if you go to https://app.sparkpost.com/account/webhooks and look at the webhooks list, do you see "MWZWEBHOOKHANDLER"? If you do, what does Batch Status says?
@Tiago Barbosa - No, mailwizz should be able to create that automatically for you.
Do you think you can PM me with app login info and sparkpost login info so that i can figure out what happens ?
What is your email? I'll send to you all access. I've updated the status field to ACTIVE on the table mw_delivery_server and now the mwz is sending by spark, but it's wrong because no webhook was created in the correct way.