# FindRoot giving error in Mathematica version 12

I was using the same code in previous version of Mathematica but unfortunately I had to update Mathematica to version 12 because I upgraded MacOS to Catalina. Now when I run my code, I get this error

And my plots all look smeared up because of numerical errors which I wasn't seeing before. Can anyone help me how to proceed?

Whole code is here:

ClearAll["Global*"]
q := 1.6*10^-19; (* Electron charge in Coulomb *)

me := 9.1*10^-31; (* Free electron rest mass in kg *)

h := 6.63*10^-34;  (* Reduced Planck's constant in J.s *)

kb := 1.38*10^-23; (* Boltzmann constant in J/K *)

FD[d_, \[Eta]_] := -PolyLog[
d + 1, -E^\[Eta]];(* Defining the Fermi-Dirac integrals *)

Nc[d_, gs_, gv_, meff_, T_] :=
gs*gv*((2*\[Pi]*meff*me*kb*T)/h^2)^(d/
2);  (* Effective band-edge DOS in d dimensions *)

n[d_, gs_, gv_, meff_, T_, \[Eta]F_] :=
Nc[d, gs, gv, meff, T]*
FD[(d - 2)/
2, \[Eta]F]*(100)^-d; (* Effective SI carrier density in d \
dimensions in cm units*)
\[Eta]S[d_, gs_, gv_, meff_, T_, v_, nd_] :=
Quiet[Chop[
FindRoot[
1/2*(n[d, gs, gv, meff, T, \[Eta]] +
n[d, gs, gv, meff, T, \[Eta] - (q*v)/(kb*T)]) ==
nd, {\[Eta], 1000000}]][[1]][[
2]]]; (* Source Fermi Level at voltage v in d dimensions*)

Lkcore[d_, gs_, gv_, meff_, T_, v_,
nd_] := ((FD[d/2, \[Eta]S[d, gs, gv, meff, T, v, nd]] +
FD[d/2, \[Eta]S[d, gs, gv, meff, T, v, nd] - (q*v)/(kb*T)] -
2*FD[d/2, \[Eta]S[d, gs, gv, meff, T, 0, nd]])/(FD[(d - 1)/
2, \[Eta]S[d, gs, gv, meff, T, v, nd]] -
FD[(d - 1)/
2, \[Eta]S[d, gs, gv, meff, T, v, nd] - (q*v)/(kb*T)])^2);
(* Quantum Inductance Kernel *)

Lk0[d_, gs_, gv_, meff_, T_] := (\[Pi]*meff*me*d)/(
q^2*Nc[d, gs, gv, meff, T]);
Lkall[d_, gs_, gv_, meff_, T_, v_, nd_] :=
Lk0[d, gs, gv, meff, T]*Lkcore[d, gs, gv, meff, T, v, nd];
t1 = LogLogPlot[{Lkall[3, 2, 1, 1, temp, 0.1, 10^16]*10^21}, {temp,
0.001, 300}, Frame -> True, FrameTicks -> True,
GridLines -> Automatic,
FrameLabel -> {"Temp (K)",
"\!$$\*SubscriptBox[\(L$$, $$k, 3 D$$]\) /l(nH/\[Mu]m)"},
BaseStyle -> {FontSize -> 15}, PlotRange -> Full,
AxesOrigin -> {Automatic, 0},
PlotLegends -> {"\!$$\*SuperscriptBox[\(10$$, \
$$16$$]\)/\!$$\*SuperscriptBox[\(cm$$, $$3$$]\)"},
PlotStyle -> {Thick, Red}]
`

Result looks like this

Earlier it used to look like this: