In the summer of 2018 Beds24 introduced a new policy where Beds24 properties would not accept a message from a remote site until that site has been whitelisted on the Beds24 manager's Link page.
The symptom of this is you visit the Channel Management page in Jomres and instead of property names in two columns associated with each other, you can see a list of property names with the options to Import/Export those properties to or from Beds24, and if you try to view a property it tells you it's not sync'd.
What you need to do is visit your Beds24 account, go to Account > Account Access and scroll down to the API Key field.
In this field click allow whitelist and then save. Once you've done that you will be able to add your server's IP number.