Error accessing the Extension Manager

Hi,
after a (test) upgrade of our site from J4.4.6 to J5.1.2 I am no longer able to access the Extension Manager under Components. I get the following error:
0 RegularLabs\Library\Http::getFromUrl(): Argument #2 ($timeout) must be of type int, string given, called in /home/betaf/public_html/fafo240717/administrator/components/com_regularlabsmanager/src/Helper/ExtensionsHelper.php on line 252

When I turn on Debug mode, I get the following details:
# Function Location
1 () JROOT/libraries/regularlabs/src/Http.php:84
2 RegularLabs\Library\Http::getFromUrl() JROOT/administrator/components/com_regularlabsmanager/src/Helper/ExtensionsHelper.php:252
3 RegularLabs\Component\RegularLabsExtensionsManager\Administrator\Helper\ExtensionsHelper::getExternalData() JROOT/administrator/components/com_regularlabsmanager/src/Helper/ExtensionsHelper.php:32
4 RegularLabs\Component\RegularLabsExtensionsManager\Administrator\Helper\ExtensionsHelper::get() JROOT/administrator/components/com_regularlabsmanager/src/Model/MainModel.php:54
5 RegularLabs\Component\RegularLabsExtensionsManager\Administrator\Model\MainModel->getItems() JROOT/libraries/src/MVC/View/AbstractView.php:159
6 Joomla\CMS\MVC\View\AbstractView->get() JROOT/administrator/components/com_regularlabsmanager/src/View/Main/HtmlView.php:41
7 RegularLabs\Component\RegularLabsExtensionsManager\Administrator\View\Main\HtmlView->display() JROOT/libraries/src/MVC/Controller/BaseController.php:697
8 Joomla\CMS\MVC\Controller\BaseController->display() JROOT/administrator/components/com_regularlabsmanager/src/Controller/DisplayController.php:31
9 RegularLabs\Component\RegularLabsExtensionsManager\Administrator\Controller\DisplayController->display() JROOT/libraries/src/MVC/Controller/BaseController.php:730
10 Joomla\CMS\MVC\Controller\BaseController->execute() JROOT/libraries/src/Dispatcher/ComponentDispatcher.php:143
11 Joomla\CMS\Dispatcher\ComponentDispatcher->dispatch() JROOT/libraries/src/Component/ComponentHelper.php:361
12 Joomla\CMS\Component\ComponentHelper::renderComponent() JROOT/libraries/src/Application/AdministratorApplication.php:150
13 Joomla\CMS\Application\AdministratorApplication->dispatch() JROOT/libraries/src/Application/AdministratorApplication.php:195
14 Joomla\CMS\Application\AdministratorApplication->doExecute() JROOT/libraries/src/Application/CMSApplication.php:306
15 Joomla\CMS\Application\CMSApplication->execute() JROOT/administrator/includes/app.php:58
16 require_once() JROOT/administrator/index.php:32

Extension Manager version: 9.0.1 - also tried reinstalling the Extension Manager
I could not find any mention of this on the forum, can you help?
Thanks,
Ornulf

Sorry, unistalled the Library Package, Library and Plugin, then reinstalled the Extension Manager. Same error...

Sorry, not on this test server, but I will try to install and upgrade on another server where I can give you access. Also, that will be a test to see if I can replicate the problem.
Give me a couple of days, I´ll get back to you when the other version is ready.

OK, got the site up and running on my other test server.
Thanks for looking into this so quickly.
Ornulf

Hmm, reinstalling the development version on my original test site did not seem to make a difference, however, when I went to Global Configuration > Regular Labs - Extension Manager and Saved the configuration there, the problem was fixed as you said.
I will make a note of this for future references, and thank you for your great support!
Ornulf