# 400: Couldn't complete the operation. Please contact support if the problem persists

**URL:** <https://community.fireblocks.com/t/400-couldnt-complete-the-operation-please-contact-support-if-the-problem-persists/1974>\
**Category:** Developer Discussion\
**Created:** [November 28, 2024, 4:16pm UTC](https://community.fireblocks.com/t/400-couldnt-complete-the-operation-please-contact-support-if-the-problem-persists/1974 "2024-11-28T16:16:12Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![telekom\_greg](https://avatars.discourse-cdn.com/v4/letter/t/b3f665/32.png) [@telekom\_greg](https://community.fireblocks.com/u/telekom_greg)\
**Post date:** [November 28, 2024, 4:16pm UTC](https://community.fireblocks.com/t/400-couldnt-complete-the-operation-please-contact-support-if-the-problem-persists/1974/1 "2024-11-28T16:16:12Z")

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Hi, I’m trying to initiate a NCW client for demo purposes. I’ve set up a proxy backend as per requirement. When trying to call the /invoke RPC endpoint via SDK initialization, I get back Bad Request. Am I doing something wrong? Note that I haven’t set up a webhook endpoint (don’t know if and how that affects the SDK init). Also, I don’t call /enable before the SDK init for the generated deviceId (again, I don’t know if I should). Can you give me some pointers?

Thanks,  
Greg

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**Author:** ![Mohammed](https://sea1.discourse-cdn.com/flex015/user_avatar/community.fireblocks.com/mohammed/32/511_2.png) [@Mohammed](https://community.fireblocks.com/u/Mohammed)\
**Post date:** [December 26, 2024, 8:06pm UTC](https://community.fireblocks.com/t/400-couldnt-complete-the-operation-please-contact-support-if-the-problem-persists/1974/2 "2024-12-26T20:06:58Z")

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HI @telekom_greg Welcome to the Fireblocks dev Community!

The invoke RPC endpoint requires an NCW SIgner user, if you used an NCW Admin it will result in errors. Have you since been able to properly use the invokeRPC endpoint?