I have an issue with a multisite setup where I can no longer login to any of the sites. They all run from separate domains.
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I have tried the solutions on previous questions to define the COOKIE_DOMAIN in the wp-config, however I receive an error saying that this already defined? I believe it may be coming from wp-super-cache plugin, however I am not 100% sure.
I have tried to rename all of my plugins the hope to deactivate them however I am still unable to login.
Any ideas?
If it's already defined then there is already a line about COOKIE_DOMAIN in your wp-config. Change that existing line from false to true. The define-function creates a named constant, and once this has been created they can't be changes (that why it's a constant).
And super-cache doesn't cache php files.