Please help us help you and fill where relevant:
LimeSurvey version:  LimeSurvey Cloud Version 6.12.2
Own server or LimeSurvey Cloud: Lime Could
Survey theme/template: Fruity twenty-three
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My survey went live this morning, and a few people have written back that they received a message saying ' due to an internal error, your response could not be saved. Please contact.... you will not be able to proceed with the survey'. 
Please can you urgently advise? 
mage of one response attached, along with my LSS file. 

Thank you!!

No need to post twice in different forums. As you are a new user your posts need to be approved by a moderator.

An error 500 usually indicates a server issue. As you seem to be a client of the SaaS service provided by Limesurvey GmbH ("Limesurvey Cloud") I highly recommend you to open a support ticket with them.

Here in the forum we are mostly users helping users. But we do not have any insights on the server configurations of LImesurvey GmbH. I think only they will be able to really help.

What sometimes can be an issue at the end of a survey is if you have a admin notification and the email can't be sent. This can cause problems.

One other point to check: Usually the responses are still stored in the database, at least partially. Have a look if the responses are there.

I see no problems:  examples.respondage.nl/?r=srhr

Of course I do not have the images.