I am having an issue with my custom icons in MGP 1.7.3. I added an icon the other day and it only showed up on one of my two iPads. Today I deleted a few and added another one and MGP isn’t displaying the updated state of my custom icons folder i.e. the deleted icons remain and the new one is absent. I have cleared and re-selected my custom icons folder in Metaserver. My folder is on my D: Drive (PC). What’s more, if I tap ‘Refresh’ they all disappear. 
Thank you for reporting this. The custom-icon synchronization path has now been investigated across both MetaServer Windows and MetaGrid Pro.
Several related issues were identified. MetaServer could retain stale icon hashes after files were added, replaced, or deleted, causing two iPads with different cached states to receive different results. Folder-monitoring errors and individual unreadable icon files could also prevent the remaining changes from being synchronized.
The MetaServer Windows fix has now been implemented for version 6.0.4. The Release build succeeds and the full automated test suite passes, including coverage for adding, replacing, and deleting icons, divergent iPad caches, invalid files, and folder-monitoring recovery.
A related MetaGrid Pro Refresh issue was also identified: refreshing the selector could replace its icon repository without correctly reconnecting the update callback, which explains why all icons could disappear after tapping Refresh. That correction is being included in MetaGrid Pro 1.7.4.
The topic has been marked as In Progress. Once both updated builds are available, verification with the same custom-icons folder and both iPads will be very helpful.
MetaGrid Pro 1.7.4 and MetaServer Windows 6.0.4 are now publicly available with coordinated custom-icon synchronization improvements.
MetaServer now validates cached hashes against the current source files, isolates individual file failures, recovers its folder watcher and reconciles additions, replacements and deletions consistently across connected iPads. MetaGrid Pro now reconnects the custom-icon repository callback when Refresh is used and distinguishes an authoritative empty folder from a failed or incomplete synchronization.
Please update both MetaGrid Pro and MetaServer and repeat the test with the custom-icon folder on the secondary drive:
- Connect both iPads.
- Add an icon and confirm that it appears on both.
- Replace an existing icon.
- Delete an icon.
- Tap Refresh on each iPad.
Please let us know whether both iPads converge on the same folder contents after every step. If they do not, capture a MetaServer support package before restarting MetaServer and identify which operation failed.
Yes!! It works. 
Thank you for confirming this, JTB. This verifies that custom-icon synchronization is working correctly in the production release.