RSA Encryption in rsa/ecb/pkcs1Padding in Csharp

I want to encrypt OTP. I got public key from AuthCert API.My string was also encypted.but it gives an error like this
{“code”:“HIS-400”,“message”:“Request is invalid. Please enter the correct data.”,“details”:[{“message”:“The OTP that you have entered is incorrect. Please try again.”,“code”:“HIS-1013”,“attribute”:{“key”:“otp”,“value”:“CibeZL4p8q+VrVZeCVFpq8X46V07kHzEJpljLCX8T7Un+lhVVCG0vdOrEt9+Ir4q1Qh9goVEtboDGUjm521RJT9pZAn0kQjsKd82luLhxRkBPvSYgSI/CHOtFuQg/XF6Wl+/zTLmV1XGoBty5wE06uKlMFbXYhMspzK3N+PtDK4=”}}]}