Failed to load registry, closing connection. 1.16.4 Bug

When I was a joining my brother modded lan server look what happened, I got ticked off about some error bug in 1.16.4, whiling joining my brother's modded lan server the error pop up my screen it said "Failed to synchronize registry data from server. closing connection" my brother tried to fix it, but he don't remember how? Please help me fix (Debug) this 1.16.4 error bug.😞