"Internal server error 500 after step 2 in install

Hello All;

I saw a thread about an “Internal server error 500” after the second step in the installation of the Mautic software. So I have a IIS 7, MySQL 5 and PHP 7. I got the install wizard started and completed Step 1 with connecting to the database. When moving to step 2 and putting the admin user and proceed to step 3, I’m getting “500 Internal Server Error”. Here is the log file:

[2017-01-15 21:20:30] mautic.WARNING: PHP Warning: include(D:HostingSpacesxcel2greatnessmarketing.ourhealthycommunity.comwwwrootvendorcomposer/…/symfony/validator/Constraints/LengthValidator.php): failed to open stream: No such file or directory - in file D:HostingSpacesxcel2greatnessmarketing.ourhealthycommunity.comwwwrootvendorcomposerClassLoader.php - at line 414 [] []
[2017-01-15 21:20:30] mautic.CRITICAL: Uncaught PHP Exception SymfonyComponentValidatorExceptionValidatorException: “Constraint validator “SymfonyComponentValidatorConstraintsLengthValidator” does not exist or it is not enabled. Check the “validatedBy” method in your constraint class “SymfonyComponentValidatorConstraintsLength”.” at D:HostingSpacesxcel2greatnessmarketing.ourhealthycommunity.comwwwrootvendorsymfonyframework-bundleValidatorConstraintValidatorFactory.php line 74 {“exception”:"[object] (Symfony\Component\Validator\Exception\ValidatorException(code: 0): Constraint validator “Symfony\Component\Validator\Constraints\LengthValidator” does not exist or it is not enabled. Check the “validatedBy” method in your constraint class “Symfony\Component\Validator\Constraints\Length”. at D:\HostingSpaces\xcel2greatness\marketing.ourhealthycommunity.com\wwwroot\vendor\symfony\framework-bundle\Validator\ConstraintValidatorFactory.php:74)"} []
[2017-01-15 21:20:30] mautic.ERROR: Deprecation: The SymfonyComponentTranslationTranslator::getMessages method is deprecated since version 2.8 and will be removed in 3.0. Use TranslatorBagInterface::getCatalogue() method instead. - in file D:HostingSpacesxcel2greatnessmarketing.ourhealthycommunity.comwwwrootvendorsymfonytranslationTranslator.php - at line 275 [] []