Screen Printed Electrodes are disposable. You shouldn't use one electrode more than one time! However for the first time you can clean them using acid solution. see the following reference:

Electroanalysis 2014, 26, 1409 – 1418

screen printed electrode is designed to be a disposable electrode

you can try to run 20 CV in 0.5 M sulfuric acid  from 0 to 1.5 V and check the electrode behavior using buffer solution

screen-printed electrodes cannot be mechanically cleaned after that is runniing.

The Analyst 126(8):1399-1403 

Effect of pre-treatment on the surface andelectrochemical properties of screen-printed carbon paste electrodes.

You might get some information from this article.

Kindly go through the article

M. Hossam Nassef, Laia Civit, Alex Fragoso, Ciara K O’Sullivan, Analyst, 133 (2008) 1736-1741.

Screen Printed Electrodes are disposable. You shouldn't use one electrode more than one time! However for the first time you can clean them using acid solution. see the following reference:

Electroanalysis 2014, 26, 1409 – 1418

Please refer my publications ( M. Balamurugan, P. Santharaman, T. Madasamy, Jonathan Claussen, C. Karunakaran, A volume miniaturized hydrogen peroxide sensor based on peroxidase activity of copper(II) chlorophyllin on zinc oxide and polypyrrole nanocomposite, Sensor Lett. 14 (2016) 665 – 672) for the pretreatment of Screen Printed Carbon Electrodes.

Please refer my publications ( M. Balamurugan, P. Santharaman, T. Madasamy, Jonathan Claussen, C. Karunakaran, A volume miniaturized hydrogen peroxide sensor based on peroxidase activity of copper(II) chlorophyllin on zinc oxide and polypyrrole nanocomposite, Sensor Lett. 14 (2016) 665 – 672) for the pretreatment of Screen Printed Carbon Electrodes. It is disposable, cost low finally washed with distilled water for several times then to run the instrument you can't get any peaks.