Couldn't load Blizzard_Collections: Missing — Mount/Pet Journal won't open

[sida]

Hello,
When I click on the Mount/Collections icon (or press the default keybind), I get this error:
"Couldn't load Blizzard_Collections: Missing"
and the Collections window does not open at all.
What I've already tried:
Disabled all third-party addons and tested with only default UI — same error still appears
Tried /reload after the error
Tried /run EnableAddOn("Blizzard_Collections") and /reload — no change
This suggests the Blizzard_Collections addon files might be missing or corrupted in my client installation. Since I can't use Battle.net Scan and Repair (this is the PandaWoW client, not a Battle.net install), could you please help me find:
Which patch/file contains Blizzard_Collections for the current client version
A link to redownload it, or instructions to verify my Data folder integrity
Thanks in advance for the help!

[Macsimka]

Hi, close game and restart launcher. Waiting for your feedback.