Carddav syncing is not working for me.

I don't know if it's a coincidence but it is possible that problems have started when I added a new contact in my phone with only a last name and a phone number. I know that contacts should have first name or e-mail but i made a mistake this time.

I tried to install PeopleSync CardDAV Client and set it up according to the

EmClient on my Windows Computer is giving me "[CardDAV] Sync of Zoho contacts/default failed due to the following error: Zoho contacts (Bad Gateway)".

Is it possible that I broke syncing by a bad contact and is there any way to repair it? I have tried to delete contacts in my phone even reset (delete) contacts in Zoho but it didn't help.