A DOI is not mandatory to cite a publication. These proceedings are also available in printed form (https://www.proceedings.com/56764.html). Create the reference for the printed version. You may add the persistent identifier, but this is also not mandatory.
Dear Jimmie Miller It is sufficient to include this conference paper (in your example) in your reference list (with as much as possible details):
Vogl, G., Fesperman, R., Ludwick, S., Klopp, R., Grabowski, A., Lebel, J., ... & Hennessey, C. (2020, October). Development of a New Standard for the Performance Evaluation of Single Axis Linear Positioning Systems. American Society for Precision Engineering 35th Annual Meeting, Minneapolis, MN, US.
If you search for this one in Google Scholar, you find the full text version and you can insert the link. A publisher like Springer include various links to their papers (the DOI link), a CAS link (if available) and a Google Scholar link, see for example: Article Identification of Possible Lipid Binding Regions in Food Pro...
(click on the DOI and you are redirected to the Springer website and then scroll to references)
Or Elsevier where you can see (in most cases) links assigned to the references to the corresponding Scopus link, a CrossRef link and Google Scholar link, see for example
Article RuBisCO as a protein source for potential food applications: A review
(click on the DOI and you are redirected to the Elsevier site)
So just properly citing the publication in accordance with for example APA is sufficient.