Surface Plasmon resonance no analyte response

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Hello Our group has been having issues with Surface Plasmon Resonance. We are working with a BioSensing setup with manual injection. For the first two or three months of use we were able to see analyte binding with repeatable results in the Pico-molar to Nano-molar range. Then all of a sudden no signal can be read for analyte binding using the same chip, carboxymethylated chip, and reagents. We were quite confused and returned the machine to the manufacturer for them to test and deep clean. We got the unit back and performed a standard BSA kit on a CM chip and see immobilization and a light analyte response, compared to response graphs we were receiving previously, but presence of the analyte signal gave us hope that the machine was fixed. However, once we moved to out desired ligand and analyte we see immobilization but no analyte response at all. Not only can we not repeat previously obtained analyte binding data we cannot see our analyte controls bind in either. We first thought it could be due to a change in protein as a different supplier was used and tested the two proteins against each other but see similar results for both immobilization but not analyte response. We have been stranded in results limbo due to this set back if anyone has any tips or has dealt with a similar issue your input would be greatly appreciated. I will include a resent SPR figure of what we are seeing. Thank you for any help that may come from this!