In most cases, yes. The role of a managed service provider is to work with vendors in each industry (accounting, healthcare, construction, etc) to establish a level of front-line training for technicians to deal with level 1 issues, and escalate higher-level issues to the vendor as needed. If the software is not on a support contract, then as long as some documentation is available support can be handled on a best-effort basis. Otherwise, you might need to re-think your long-term strategy and consider a more modern solution.