Call to a member function addLink()

When I install the VTENEXT CRM I have this error:

Fatal error: Uncaught Error: Call to a member function addLink() on bool in \modules\ModComments\ModComments.php:103 Stack trace: \modules\ModComments\ModComments.php(154): ModComments::addWidgetTo(Array) \install\CreateTables.php(77): ModComments->addWidgetToAll() \install.php(63): include('D:\home\h461888...') {main} thrown in \modules\ModComments\ModComments.php on line 103

I did some debug and saw that:
\modules\ModComments\ModComments.php at line 102
$modCommentsModule = Vtiger_Module::getInstance('ModComments');
$modCommentsModule is null è nullo and addLink is impossible to run

also in:
\modules\MyNotes\MyNotes.php at line 240
$currentModuleInstance = Vtecrm_Module::getInstance('MyNotes');
$currentModuleInstance is null and setRelatedList is impossible to run

getInstance go to search on db vte_tab ModComments and MyNotes but this 2 records not exists.

I added a "IF" before to verify the variable is not null and the installation was completed.

But when I make a login in one box I have error: ModComments module is not active

Thanks

yes a lot of times also removing the database and file config.inc.php

denis wrote: Well, you have to start again from the beginning so removing only config.inc.php is not enough

can you explain me how? I delete the database and removed config.inc.php and copying again the hash_version.txt on the root.

is it not sufficient?