Attachments copied but not opening on new Manager platform

Hi everyone,

My firm has recently merged with a larger firm. We are both using Manager as accounting software for our clients. I recently backed up the accounting file of one of my clients to bring it under the Manager plaform of the new larger firm. The backup went well and smoothly and I can see all the attachments came through. However, I can’t open any of the attachments.

Here is the message I’m getting:

Does anyone know how to fix this ?