Good basic knowledge about Zigbee regardless if read it before or after starting is also to try to follow all the advice here → Guide for Zigbee interference avoidance and network range/coverage optimization
In addition, check out the read the best practices to avoid Zigbee pairing/joining/connection difficulties
There are all in all many simple actions that can and should take to workaround known Zigbee issues.
Most problems are not specific Zigbee gateway solutions so most tips apply to all setups/environments.