[TYPO3-user-registration] sr_feuser_register 3.1.3 no image thumbnail

[rsbrux]

I have been trying to upgrade my typo3 4.5 installation from sr_feuser_registration 2.6.1 to 3.1.3 for months now.
One of the sticking points is the display of the user's profile picture.
Where the registration or profile edit page used to show a thumbnail of the profile picture uploaded by the user, only the file name appears.
I have the same results with both the standard template supplied with the extension and with my customized template.
How can I find out and fix what is wrong?
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Typo3 4.5.41
PHP 5.3
mySQL 5.4.39
Windows 8 x64