Unity IronSource Facebook mediation issue "No adapters ready to show"

[Tomasz Woźniak 1981]

Hi,
I have integrated mediations for IronSource SDK (UnityAds, AdMob, AppsLovin, Facebook, etc) in Unity Android and iOS game.

All working fine except for Facebook.

Despite the correct logs from integration helper:

--------------- Facebook --------------
Adapter 4.3.4 - VERIFIED
Adapter - VERIFIED
SDK Version - 5.3.1
* Activities *
com.facebook.ads.AudienceNetworkActivity - VERIFIED
com.facebook.ads.internal.ipc.RemoteANActivity - VERIFIED
* Services *
com.facebook.ads.internal.ipc.AdsProcessPriorityService - VERIFIED
com.facebook.ads.internal.ipc.AdsMessengerService - VERIFIED
Facebook - VERIFIED


when I try to load Interstital or Rewarded Video I receive error:

Interstitial Show Fail - showInterstitial failed - No adapters ready to show

Please help.
Thanks in advance.