Exception: Field currentActivity or type signature not found

i was trying to implement StartApp ad network to my android application and i had this error when i click on the button to show the ads :

Exception: Field currentActivity or type signature not found
UnityEngine._AndroidJNIHelper.GetFieldID (System.IntPtr jclass, System.String fieldName, System.String signature, System.Boolean isStatic) (at <2f4b1d01c9a3419997bae38a98e4dc24>:0)

The code :

public Text todayEarnings;
public Text totalEarnings;

public void OnMouseDown()
    {
        gameObject.GetComponent<Collider2D>().enabled = false;
        gameObject.GetComponent<Animator>().enabled = false;
        todayEarnings.enabled = false;
        totalEarnings.enabled = false;


            var ad = AdSdk.Instance.CreateInterstitial();
            ad.RaiseAdLoaded += (sender, e) => ad.ShowAd();
            ad.RaiseAdVideoCompleted += (sender, e) =>
            {
                SceneManager.LoadScene("playScene1");
            };
            ad.LoadAd(InterstitialAd.AdType.Rewarded);
        
       
    }

same error any solutions??