Can’t bind to ‘disabled’ since it isn’t a known property of ‘li’

The <li> element doesn’t have a disabled property.
Either a component or directive that you expect to be applied to <li was actually not applied, or perhaps the disabled attribute should be set instead of the property

<li [attr.disabled]="pager.currentPage > 1 ? true : null">

null is to get the attribute removed in case the condition is false. A boolean false would lead to

<li disabled="false">

which might not what you want. With null you get

<li>