When navigating to the Juniper MIB SNMP explorer site under Juniper Evolved heading & attempt to download the MIB for 23.4R2 as a zip file.
But it downloads as a tar file.
https://apps.juniper.net/mib-explorer/download?software=Junos%20OS%20Evolved
We have taken up the issue via an internal PR to correct the files.
For now, JTAC can downloaded the tar file, uncompress it, zip it again & uploaded to case as zip.