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Your LimeSurvey version: [see right hand bottom of your LimeSurvey admin screen]
Own server or LimeSurvey hosting:
Survey theme/template:
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I need to do Reverse Navigation. I set the option " Reverse Navigation" on. When I run the questionary on the left corner appears the " Back" option button. But it doesn´t work. The color of the button is grey which means isn´t available. Something elese to do? 

Unfortunetaly you did not respond to any of the basic questions like, what is your Limesurvey version, is it installed on an own server or is it hosted by Limesurvey GmbH, which survey theme you use...

So again:
1. What is your Limesurvey version?
2. Do you host it yourself (Limesurvey Community Edition) or is it a SaaS services hosted by Limesurvey GmbH? Or is it a University installation?
3. What is the survey theme/template that you are using for this survey?

Can you activate a little test survey and post the link here so we can have a look?

Here we go!
What is your Limesurvey version? ==> Versão 3.13.1+180629
2. Do you host it yourself (Limesurvey Community Edition) or is it a SaaS services hosted by Limesurvey GmbH? Or is it a University installation? ==> hosted in our Datacenter
3. What is the survey theme/template that you are using for this survey? ==> bootswatch (the only available)

Can you activate a little test survey and post the link here so we can have a look? tjba.jus.br/enquete/index.php/928318?lang=pt-BR or tjba.jus.br/enquete/index.php/949827?lang=pt-BR

But I have a new information! I reactivate the first survey just changing the option "Reverse Navigation" and it works on this survey! But on the 2nd one it doesn´t.
So, I still have an issue to solve!

I confirm that it works for:
tjba.jus.br/enquete/index.php/928318?lang=pt-BR

In the second research you have more problems than just the back button not working.

E.g. I can't insert the telphone number in the requested format, because it doens't allow that many digits. What about mobile phones? Not allowed? Maybe because it is a public service and they would need to have a fixed office phone? I think Bahia should have the digit 9 for mobile phones as well now, right?

So as one works and the other one doesn't, I can only assume we are talking about an issue with this specific survey.

My first suspicion that it was an issue with the theme seems not be the case, because if so it shouldn't work in any of the surveys.

One other thing, on the welcome page of the second link the image doesn't show, but only an error of the missing image.

Try export the survey and import it again, and before a data integrity check would probably also be a good idea.

Right now, I have not real other idea. Maybe Denis, Tpartner or Joffm can come up with something.

The button is not disabled, the grey colour is set by the theme CSS.

I suggest updating to the latest 3.x version and retesting.

Oh, yes, Tpartner. Totally forgot my rant about the old version.

Your Limesurvey version 3.13.1+180629 is almost 4 years old and thus hasn't received any updates, bug fixes and security patches since mid 2018. In times of LGPD (Brazilian Data Protection Law) I think this is even more problematic, especially for a public institution that is potentially collecting private data with a software that hasn't been updated or patched for 4 years.

Update to the lates version of LS 3.x.

Tks a lot Holch!

The missing image is because I made a copy but I forgot to upload the image!

But I would ask you what is a data integrity check and how I perfome it?

By the way I already asked the support team to update the version!

www.limesurvey.org/manual/Check_data_integrity/en

But the integrity check might not really be relevant for your issue.

I think I had actually more the "Survey logic view" in mind. You can find it under "tools" within your survey and it will show you the logic of your survey and you can check if something is wrong there.