Inmobi.com "ad request successful but no ad served"

When I try to load an interstitial with inmobi.com and most of the times I get the error "ad request successful but no ad served". Why is this happening? Any solution for this? It works well with testing ads when set to "Test mode" in the website. Will this be because inmobi has not enough providers to display ads at that moment?

I asked Inmobi support page but they don't answer. I am starting to regret moving from admob to inmobi.

This is the code I use:

JSONObject consentObject = new JSONObject();
try {        
    consentObject.put(InMobiSdk.IM_GDPR_CONSENT_AVAILABLE, true); // Provide correct consent value to sdk which is obtained by User        
    consentObject.put("gdpr", "1"); // Provide 0 if GDPR is not applicable and 1 if applicable        
    //consentObject.put(InMobiSdk.IM_GDPR_CONSENT_IAB, “<<consent in IAB format>>”); // Provide user consent in IAB format
} catch (JSONException e) {        
}


InMobiSdk.init(this, "My InMobi Account ID here", consentObject); 
long MyPlacementID = 1234566789L;  //My Placement ID here as long
mInterstitialAd = new InMobiInterstitial(this, MyPlacementID,  new InterstitialAdEventListener() { 
@Override
public void onAdLoadSucceeded(InMobiInterstitial inMobiInterstitial) {
    super.onAdLoadSucceeded(inMobiInterstitial);
    if (inMobiInterstitial.isReady()) {
        mInterstitialAd.show();
}
@Override
public void onAdLoadFailed(InMobiInterstitial inMobiInterstitial, InMobiAdRequestStatus inMobiAdRequestStatus) {
    sError = inMobiAdRequestStatus.getMessage();
    Here I get error:  "ad request successful but no ad served"
}

I emailed the support team and they answered that is shown if they don't have any ad to be displayed (maybe for my location or for my time). So, it is just that they run out of ads to be displayed. If I try it many many times then I may get one ad. So it is a server problem. Not enough clients to pay for ads. It is a pity.