OC 2.0.1.1. suddenly-edit orders-Syntax error:JSON..

Hello,
I can't edit orders. Gives syntax error: syntaxerror: json.parse: unexpected end of data at line 1 column 1 of the json data ok. And loading very slow when click on "edit". According the hosting company openbay plugin try to load. But I've never install/enable openbay or amazon, ebay, etc.
This is strange, because the shop is 1 year old and everything was ok until 1 week. I already tried all tips which I found in Opencart forum (API, maintenance mode off, api_id is the same value in oc_api_settings) but couldn't find any solution.
I asked the hosting company and they said that they didn't make any changes.

The store haven't any extensions or additional moduls installed. Just clean OC instalation +Journal theme. Haven't .htacess file. Have ssl. I've not made any changes (except add new products).
Please, help!

Hi sadlady,

The JSON error you will get for most anything...

Things you can do:

See if your current IP address is the same one as in the table.
Delete and recreate your API information
Check your OpenCart files to make sure that they have not been corrupted

Hi Sadlady!

First be happy because this error could be fixed

As said in earlier answer that there could be many reasons for it and some steps are suggested, follow them if it resolves your issue, if not:

- Check that language files don't have invalid UTF-8 characters (May look like strange non-readable symbols)

If it resolves the issue good, otherwise:

- Replace admin/controller/sale/order.php with that of found in Opencart version 2.0.3.1

Thank you, Randem

See if your current IP address is the same one as in the table.
I'm not sure which table do you mean.
Delete and recreate your API information
I tried but nothing heppend.

Check your OpenCart files to make sure that they have not been corrupted
Do you mean I need to check any files?One by one? How do I know that they are corrupted?

Thank you, munirasim
I'll try your advice.