You recently received a notice from Octopia stating that it will no longer support managing activity feeds via the SOAP API and that you must switch to the REST API.
If you haven't already done so, go to this URL, click "I'm using a feed aggregator," and follow the "My aggregator only requests my SellerId" procedure, selecting Market Invaders as your aggregator.
Once this process is complete, you can open a ticket with our customer support team to let us know that you've completed the steps so that our technical team can perform the migration.