Being unable to reproduce this in the previous few snapshots, this is most likely an issue in the recent launcher version.
On game load, /reload, or data pack enabling or disabling, any errors in parsing of data pack components will not display detailed errors.
However in the game log it will still print the detailed error. https://hastebin.com/egafetefav.sql
I believe there used to be an issue ticket on this not too long ago which was fixed and resolved, but I was unable to find it again. If someone can find it, they should most likely close this as a duplicate and reopen that issue.
How To Reproduce
Create data pack with a function file in it.
Write anything not a proper command into it.
Run /reload.
Resolved it as duplicate of MCL-12594 because that report is more generic.