I am having exactly the same issue, several contexts routed to subfolders, I came across the cookie path earlier and tried it [because it was defaulting to a path users's should not have access to] but when I add the / if a user tries to log in they get blank pages on the front end!
here is the post about it in stack exchange:
http://stackoverflow.com/questions/32080915/modx-revolution-2-3-5-login-snippet-users-are-not-getting-sessions-after-logg/32081024#32081024
I'm having a strange issue with a new modx site - web users are not getting sessions after logging in. I'm sure they are authenticating correctly but modx does not seem to be setting the session. I think it has something to do with context access.
I have 3 contexts, web, French & English I have user groups and resource groups which has access to the appropriate contexts.
here is my login snippett:
[[!Login?
&loginTpl=`LoginTpl`
&logoutTpl=`LogoutTpl`
&errTpl=`lgnErrTpl`
&loginResourceId=`91`
&logoutResourceId=`5`
&contexts=`English,French`
]]
users are not being granted access to the web resource as it will be used for internal documentation.
NOW, everything appears to behave normally, if you enter incorrect credentials in the login form, you get a login error. If you enter correct credentials you get forwarded to the correct resource [91] BUT the user does not have a session [[!+modx.user.id]] returns 0 for the anonymous user. AND if I look at my browser cookies, all I have is the default php session cookie and no modx session cookies. curiously, the cookie path is /docs/ which is the base_url for the web context. if I change the cookie path to / in modx then all pages are blank for the user!!
What is causing the problem here??