When you are trying to access the Typo3 install console you need to create an empty file called “ENABLE_INSTALL_TOOL” within /typo3conf/ folder. In some cases Typo3 deletes this file everytime you want to access the install console.
You can solve this by editing the file and insert the line “KEEP_FILE”. After that, try to access the install console again and it will work.
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If your Typo3 back end is broken (looks messy like the css is missing) after you did an update of your Typo3 installation (f.e. from version 4.1.3 to 4.4.1) head over to the /typo3conf/ext folder and look for an extension called “mn_ff3_be_bugfix”. Back it up to your local computer and then delete it on your webserver. Now load the back end again and now it should work.