is there any error in the server.log when this packages is loaded, i.e. during startup of IS?
Is this package dependent on another package which is not existing on the new IS?
You can check the manifest.v3 in the root of the package for informations on package dependency.
This might be due to deprecation of certain packages over time.
How was the package deployed, by Publish/Install inbound or by Deployer?
Please note that the migration from wM 8.2 to wM 10.3 is quite huge jump, which should been handled by intermediate migrations to wM 9.5 and wM 9.12 as there is no direct migration path for migrating from wM 8.2 to wM 10.3.
Are the files in the package readable by the user running the IS?
Additionally please note that IS has a different directory structure since wM 9.6, the real IS is no longer under IntegrationServer/ itself, but under IntegrationServer/instances/default/ instead.