From the Joytech website - 2-3 months expected life span - looks like your out of warranty OP
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E-Cigarette Product Warranty & Safety Information
Warranty
16.1 All hardware comes with a 28 day parts warranty, unless stated otherwise in the individual product listings or manual, this does not cover any atomizer heads, wire or wicking material. We are not responsible for any damage through improper use or coil builds. It is the user’s responsibility to ensure they have significant knowledge of coil resistances. Mains chargers and USB leads have a 12-month warranty, which covers the component parts; this does not cover damaged wiring or improper use.
16.2 You should be aware that our electronic cigarette atomizers and batteries, although made to the highest quality, may fail or degrade over a period of time. An electronic cigarette atomizer's expected lifespan is around 7-14 days depending on usage and an electronic cigarette battery's expected lifespan is 2-3 months. This is not a guarantee that you will ‘like’ the Electronic Cigarette, simply that it will function as described within the specified timeframe.
16.3 All replacement atomizer heads are sold as a single use disposable items and are covered by our DOA (dead on arrival) warranty. This means, that from date of receipt the buyer has 48 hours to ensure the goods are in good working order and report any faults.
16.4 Any replacement parts are warranted from the date of delivery of the original order.
16.5 The warranty in clause 16.1 to 16.4 does not apply to any defect in the Products arising from:
(a) fair wear and tear;
(b) wilful damage, abnormal storage or working conditions, accident, negligence by you or by any third party;
(c) failure by you to operate or use the Products in accordance with the user instructions;
(d) failure by you to carry normal maintenance of the Products including regular cleaning of components and connectors;
(e) any alteration or repair by you or by a third party who is not one of our authorised repairers; or
(f) any specification provided by you.
16.6 This warranty is in addition to, and does not affect, your legal rights in relation to Products that are faulty or not as described. Advice about your legal rights is available from your local Citizens' Advice Bureau or Trading Standards office.