The Bren mod uses the same fabric-networking-api-v1 libraries that are present in FFAPI 1.20.1

https://modrinth.com/mod/bren
https://www.curseforge.com/minecraft/mc-mods/bren

https://github.com/SniffVillage/Bren

But these libraries do not work at all in the game. Although everything should work fine.
What could go wrong?
The location of the network class?
A mod problem? Or FFAPI?

What can be done to identify the exact problem?
I've checked almost all the code of the mod and FFAPI and found nothing that doesn't match.

Code for a mod that doesn't work:
https://github.com/SniffVillage/Bren/blob/main/src/main/java/nl/sniffiandros/bren/common/network/NetworkUtils.java

The classes used are from FFAPI library:
https://github.com/Sinytra/ForgifiedFabricAPI/blob/1.20.1/fabric-networking-api-v1/src/main/java/net/fabricmc/fabric/api/networking/v1/PacketByteBufs.java
https://github.com/Sinytra/ForgifiedFabricAPI/blob/1.20.1/fabric-networking-api-v1/src/main/java/net/fabricmc/fabric/api/networking/v1/ServerPlayNetworking.java

I know that Sinytra won't update as often anymore to fix small mods, but maybe it's possible to fix this bug without modifying files from FFAPI side?
Video

Nah bren mod is completely abandoned. No way author will make any compatiblity by himself

Please specify what the issue is.