Missing Login Page

Hi,
Something has just come to light today - when a user (or me!) clicks any login link....all they see is the text "Welcome, Please Sign In" on the login page - nothing more.

This may well have been going on for a while, as pretty well all of my customers seem to just go off to PayPal to pay (using Express Checkout) and not bothering to login. I'm really not sure what has happened - I change things around quite a lot, but I don't recall changing anything that would have affected this page. Certainly I haven't meant to change it!!

I have Snapshot installed, that I run every 12 hours. I've looked at the last few days and come up with nothing as yet. Now, I know the login page has been working, as I've used it myself to log in to customers' accounts and test accounts. I can't remember when I last did this, though. I shall continue to look through my File Watch logs, but in the meantime - does anyone have any idea what file(s) I may have inadvertently mucked up, probably by leaving off a ";" or something?

I've attached a wee jpg of the screen, if it's not obvious what I'm on about. Simplythebestontheweb.co.uk if you want to view the source.

TIA,
Gavin

What you're seeing is a "partial whitepage", which implies that there's a debug-log file in your store's /logs directory.

Yes, there are two logs from today, chock full of "GET"s and "POST"s etc. They call themselves "Mar-2014" logs, so I'm not sure there's anything untoward going on in there. Any idea of a keyword I could search for? There's one sort of multiple entry that looks a little curious;
"176.34.107.34 - - [15/Mar/2014:23:34:19 +0000] "POST /cgi-bin/php?%2D%64+%61%6C%6C%6F%77%5F%75%72%6C%5F%69%6E%63%6C%75%64%65%3D%6F%6E+%2D%64+%73%61%66%65%5F%6D%6F%64%65%3D%6F%66%66+%2D%64+%73%75%68%6F%73%69%6E%2E%73%69%6D%75%6C%61%74%69%6F%6E%3D%6F%6E+%2D%64+%64%69%73%61%62%6C%65%5F%66%75%6E%63%74%69%6F%6E%73%3D%22%22+%2D%64+%6F%70%65%6E%5F%62%61%73%65%64%69%72%3D%6E%6F%6E%65+%2D%64+%61%75%74%6F%5F%70%72%65%70%65%6E%64%5F%66%69%6C%65%3D%70%68%70%3A%2F%2F%69%6E%70%75%74+%2D%64+%63%67%69%2E%66%6F%72%63%65%5F%72%65%64%69%72%65%63%74%3D%30+%2D%64+%63%67%69%2E%72%65%64%69%72%65%63%74%5F%73%74%61%74%75%73%5F%65%6E%76%3D%30+%2D%6E HTTP/1.1" 301 1191 "-" "Mozilla/5.0 (iPad; CPU OS 6_0 like Mac OS X) AppleWebKit/536.26(KHTML, like Gecko) Version/6.0 Mobile/10A5355d Safari/8536.25""

That's as far as I've got, so far. The IP address above is apparently caramel-shop.co.uk in Ireland - don't know them, but their website looks genuine... I haven't a clue what that POST command is supposed to be doing...

Those logs are the access logs. The /logs directory I was referring to is part of your Zen Cart's installation. For example, if the file-system path to your Zen Cart's index.php file is c:/xampp/htdocs/test, look in c:/xampp/htdocs/test/logs for files named myDEBUG*.log; those will have the debug information that will identify why your login page has crumbled.

Thanks - I sort of got that; I was wondering if the /logs files may have evidence of some nasties going on. My DEBUG log files are in /cache..but because of a problem with some code elsewhere (Dr Byte has posted a get-round, but it didn't work for me) I get thousands of these, all with pretty much the same non-destructive error (PHP Warning: strlen() expects parameter 1 to be string, array given in /home/MYSITE/public_html/includes/functions/functions_general.php on line 153).

This being the case, I clear out my cache regularly - without looking at the logs. My earliest log is currently from 14th March but I have so many it takes forever to trawl through them.

I've also been looking at file change dates - there are only a limited number of files for me to look at and I'm going through them, comparing current files with previous versions (I run Genie Timeline, so I have a number of versions to look at). Found nothing as yet. I also have some backups (probably not exactly when I want, but that's life according to Mr Sod), so all is not lost - but I really want to find out what has gone wrong, so I don't do it again; not just fix the problem!

If I find the cause of the problem and it's interesting, I'll post what went wrong, so it may help others.

OK - I found the cause of the problem. And it's interesting, so here goes.

I have a module on my site - 'Social Login'. As it sometimes doesn't like connecting, I thought I'd disable this...so I turned off display of the sidebox containing it. Unfortunately....this totally mucked up tpl_login_default.php, so I couldn't get any login! So for the moment, Social Login is back....until I have time to remove the code so it doesn't affect standard usage.

This is, of course, why I couldn't find any sign of anything wrong when looking at datestamps - no file had been changed, it's just that when Social Login is installed...you have to display the sidebox! (Not very friendly!).