TypeError: JwtStrategy requires a secret or key not working in production

Question

I had a lot of research and I keep getting the same error. I'm pretty sure that it has something to do with ConfigModule because the app works well when I launch it in localhost, but when I execute it in production I get -> TypeError: JwtStrategy requires a secret or key (means the app can't see the .env secret variable I think) after dig into several webs I share the module that is doing all this:

import { Module } from "@nestjs/common";
import { APP_GUARD } from "@nestjs/core";
import { AtGuard } from "@enlazo/nestjscommon/dist/guards";
import { ConfigModule } from "@nestjs/config";
import { DatabaseModule } from "@enlazo/bd_ibm/dist";
import { AppDashboardDesarrolloController } from "./app-dashboard-desarrollo.controller";
import { AppDashboardDesarrolloService } from "./app-dashboard-desarrollo.service";
import { MailModule } from "@enlazo/mail/dist";
import { AtStrategy } from "@enlazo/nestjscommon/dist/strategies";
import { JwtModule } from "@nestjs/jwt";

@Module({
    imports: [DatabaseModule, ConfigModule.forRoot({ isGlobal: true }), MailModule, JwtModule.register({ secretOrPrivateKey: process.env.AT_SECRET })],
    controllers: [AppDashboardDesarrolloController],
    providers: [
        AppDashboardDesarrolloService,
        AtStrategy,
        {
            provide: APP_GUARD,
            useClass: AtGuard
        }
    ]
})
export class AppDashboardDesarrolloModule {}

The Atguard file:

import { ExecutionContext, HttpException, Injectable, UnauthorizedException } from '@nestjs/common';
import { Reflector } from '@nestjs/core';
import { AuthGuard } from '@nestjs/passport';
import { ErrorDto, Notification } from '../dto';

@Injectable()
export class AtGuard extends AuthGuard('jwt') {
    constructor(private reflector: Reflector) {
        super();
    }

    canActivate(context: ExecutionContext) {
        //   console.log("AtGuard");

        const isPublic = this.reflector.getAllAndOverride('isPublic', [
            context.getHandler(),
            context.getClass(),
        ]);

        if (isPublic) return true;

        return super.canActivate(context);
    }

    handleRequest(err, user, info) {
        // console.log("JWT AUTH", err, user, info);

        // You can throw an exception based on either "info" or "err" arguments
        if (err || !user) {
            if (info) {
                if(info.name == "TokenExpiredError") {
                    throw new UnauthorizedException(new ErrorDto("accessTokenExpired", Notification.warning, false));
                }
                throw new UnauthorizedException(new ErrorDto("Error de autenticación", Notification.warning, false));
            }
            throw err;// || new UnauthorizedException("accessTokenExpired");
        }
        return user;
    }
}

And finaly the Strategy:

import { Injectable } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { PassportStrategy } from '@nestjs/passport';
import { ExtractJwt, Strategy } from 'passport-jwt';
import { JwtPayload } from '../types';

@Injectable()
export class AtStrategy extends PassportStrategy(Strategy, 'jwt') {
  constructor(config: ConfigService) {
    super({
      jwtFromRequest: ExtractJwt.fromAuthHeaderWithScheme('Enlazo'),
      secretOrKey: config.get<string>('AT_SECRET'),
    });
  }

  validate(payload: JwtPayload) {
    return payload;
  }
}

Note that the first file I share is importing the next two from a dependency