Node Express Mongo Vercel – How to create PDF from HTML and send in email (nodemailer)? This worked fine until I migrated from Heroku to serverless

employeesRouter.route('/newreview/:employeesId')
    .put(cors.cors, (req, res, next) => {
        var options = { format: 'Letter' };
        var html = email.reviewStatus(
            req.body.name,
            req.body.review.date,
            req.body.review.store,
            req.body.review.effectiveDate,
            req.body.review.currentRate,
            req.body.review.newPayrate);

        pdf.create(html, options).toFile(`./${req.body.review.store}status.pdf`, function (err, res) {
            if (err) return console.log(err);
            console.log(res); // { filename: '/app/status.pdf' }
        });
        console.log(req.body.review);
        //add rating
        setTimeout(function () {
            const storeEmail = getEmail(req.body.review.store);
            const score = req.body.review.score;
            const mailDataPassChange = {
                from: 'Wenventure Inc <[email protected]>',  // sender address
                name: 'Wenventure Inc',
                to: req.body.email,
                attachments: [
                    {
                        filename: `${req.body.review.store}status.pdf`,
                        path: `./${req.body.review.store}status.pdf`,
                    }
                ],
                cc: storeEmail,   // list of receivers
                subject: `Your Performance Review -${req.body.review.date}`, // Subject line
                text: `New Review!`, // plain text body
                html: email.reviewMessage(`New Performance Review!`, req.body.name, req.body.review, score) // html body
            };
            transporter.sendMail(mailDataPassChange, function (err, info) {
                if (err)
                    console.log(err)
                else
                    console.log(info);
            });
        }, 5000);
        Employee.findByIdAndUpdate(req.params.employeesId, {
            $set: {
                nextReview: req.body.nextReview,
                lastReview: new Date(),
            },
            $push: { history: req.body.review }

        })
            .then((employees) => {
                res.statusCode = 200;
                res.success = true;
                res.setHeader('Content-Type', 'application/json');
                res.json(employees);
            })
            .catch((err) => next(err));
    })

I need to create a pdf from the html and then send this report via node mailer. I dont need to store the pdf anywhere just need to attach it to an email and send.
This worked fine when it was on Heroku, but once I migrated to Vercel it wont work any more. Is it because I can’t create new files in vercel? If so, how do you do it?