Hey @Anna1_1 - thanks for getting in touch! Generally, when it comes to callback URLs we would recommend structuring them as described in our guides, but it shouldn’t really have an impact on the data being sent to that callback URL.
Is this affecting all of the stores the custom app is installed on? If so, I could take a look at an example X-Request ID for one of the stores where the callbacks had initially gone through and then stopped/started. If you have a timeline for when the callbacks didn’t seem to be triggered (specific day/time), this would also help me track down what could be happening here. Essentially, we’d just need an example ID related to where the API was functioning correctly on one of the stores where this is happening and can work backward from that in our logs.
Happy to clarify anything on our end - hope to hear from you soon.