Error creating/requesting Network matches on WebGL.

Steps to reproduce:
1. Open attached project and configure Multiplayer settings using Unity services (set "Max players per room" to 5 or any other positive value and click "Save").
2. Select "WebGL" as a target platform in "Build Settings".
3. Create a new folder inside of the project, name it "Builds" and press "Build" button inside of the Editor.
3. After the building process is finished, navigate to the "Builds" folder and open newly created HTML file with a browser.
4. Select field named "New room name" and enter any string value, for instance, "abc".
5. Select the first field named "Domain" and enter any integer value, for instance, "12345".
6. Press "create room" button.
7. Notice that the "Development Console" outputs:

"Request error: Unknown error.
Raw response:
Create match failed"

8. Select the second field named "Domain" and enter the same integer value that was entered during the fifth step.
9. Press "List rooms" button.
10. Notice that the "Development Console" outputs:

"Request error: Unknown error.
Raw response:"

11. Repeat the same steps with Standalone and the Editor.
12. Notice that the "Development Console" outputs:

"Create match succeeded" (in the 7th step) and "Number of matches 1" (in the 10th step).

Expected result:
Creating/requesting Network matches on WebGL should work as fine as on other platforms.

Reproduced with:
5.1.0f3, 5.2.4f1, 5.3.4f1, 5.3.5f1, 5.3.5p6.

Cannot reproduce with:
5.2.4f1.
5.4.0b24, because a overhaul of the matchmaking API was made.

Note:
GIF attached.