Please help as this issue is quite frustrating.

Using Forge 1.12.2-14.23.5.2838

Following Mods:
AmbientEnvironment-1.0.1
animania-1.12.2-1.6.2
Aquaculture-1.12.2-1.6.8
BetterFoliage-MC1.12-2.2.0
BiomesOPlenty-1.12.2-7.0.1.2439-universal
ConquestReforged-3.0.2-mc1.12.2
CraftStudioAPI-universal-1.0.1.95-mc1.12-alpha
CTM-MC1.12.2-0.3.3.22
Custom-Mob-Spawner-Mod-1.12.2
Dynamic-Surroundings-Mod-1.12.2
DynamicTrees-1.12.2-0.9.5
DynamicTreesBOP-1.12.2-1.4.1e
Electroblob's+Wizardry+-+4.1.4+-+MC+1.12.2
EnhancedVisuals_v1.2.4_mc1.12.2
Exotic+Birds+1.12.2-2.2.1
Forgelin-1.8.3
iceandfire-1.8.0
llibrary-1.7.19-1.12.2
millenaire-1.12.2-7.2.1
Mo-Creatures-Mod-1.12.2
music_player-1.12.2-2.0.3.31
nature-overhaul-1.3.1
OreLib-1.12.2-3.5.2.2
Patchouli-1.0-20
randompatches-1.12.2-1.13.0.0
RoguelikeDungeons-1.12.2-1.8.0
ToughAsNails-1.12.2-3.1.0.139-universal
u_team_core-1.12.2-2.2.4.107

UPDATE: It seems like DynamicTrees is not compatible with ConquestReforged. Is there a way to make them compatible, so that the trees fall over again?

Mod compatibility is very very hard with a complex mod like Dynamic Trees. So unless you can find the exact methods responsible for this, it'll probably be left unfixed.

I'm having the same issue and I don't use Conquest Reforged.

We share these following mods:
animania-1.12.2-1.6.2
CraftStudioAPI-universal-1.0.1.95-mc1.12-alpha
Dynamic-Surroundings-Mod-1.12.2
DynamicTrees-1.12.2-0.9.5
Electroblob's+Wizardry+-+4.1.4+-+MC+1.12.2
Forgelin-1.8.3
iceandfire-1.8.0
llibrary-1.7.19-1.12.2
millenaire-1.12.2-7.2.1
OreLib-1.12.2-3.5.2.2

Perhaps it's one of these? I'm doubtful however, because none of these aforementioned mods seem like they would/should have any conflict.

EDIT: What I've noticed when traveling around test worlds is that I some of the trees are not Dynamic, as in, they're just vanilla trees. In fact a lot of them are. Those are the specific trees that will not fall when chopped. You must cut them all manually like in vanilla.

Perhaps there is a setting we can change to force world gen to only spawn dynamic trees?? Also I'm not using any other world gen mod such as Far From Home, OTG, or BoP.

Seems like the OP's issue is an incompatibility with ConquestReforged. DrGetgood please narrow the mod conflict down to a single mod so it can be better addressed. Divide and conquer your modlist until you find the mod. When you find the conflict then please submit an issue.