Is there a router / switch between 2 forests? if your answer is yes then enable AD ralated ports on that device. If there is a VPN communication between forests, then reestablish site-to-site connectivity. If I'm at your place I'll disable unwanted NICs first, because multi-homed network in recommended on DCs as per Microsoft.
There is one more tool to check policies that are applied on PC and users with RSOP.msc. Select Computer settings to check policies that are applied on Computer and User settings for user policies.
In single DC environment you have 2 options to fix issues the one you have.
1. If you have backup of the crashed DC then you can install another DC with the same details and perform authoritative restore.
2. If no backup is there, then start from scratch and build domain again.
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