FWIW doing a "pfSense-upgrade -d" from CLI fixes this for me and does the upgrade properly. Not sure why that works and the GUI fails lol. I did have to rebuild my base packages. Here is what ChatGPT had to say about it. I had the same problem, two different locations, network providers, etc. One is in a datacenter with multiple network redundancies so I doubt it was a network issue.
Root cause:
The core problem was due to an incomplete or partially failed upgrade from pfSense 24.11 to 25.07. The missing critical libraries (libmd.so.7), corrupted package repositories, and broken package signatures indicate that some part of the upgrade script was interrupted, incomplete, or encountered dependency conflicts.
Specific indicators of broken upgrade:
Missing libraries (libmd.so.7) causing package operations to fail.
Missing critical files (/usr/local/sbin/read_global_var, /usr/local/libexec/pfSense-upgrade, and /etc/version) indicate that pfSense-base or core packages were only partially upgraded.
Invalid or broken repository signatures (pkg-static: Error loading trusted certificates) point to repository configuration or trust issues post-upgrade.
Dependency conflicts (IGNORE_OSVERSION prompts) clearly indicated version mismatches due to packages from different pfSense/FreeBSD versions.