Things you should do: You should probably write a conclusion by restating the problem to get people thinking about it again or summing up your reasonings and points. When it comes to problem and solution essay's you need to make sure to know the answer to your problem but also be able to support it and wrapping it up in your conclusion is important because it gives a summary of the points you're trying to make. For example, list the points you were trying to make and like I said to summarize what was said in the introduction of your essay. But, if you want to go above and beyond try helping or giving advice to someone who has a similar problem, however this also depends on the problem being asked.
Things you shouldn't do: When writing this type of essay, you should really avoid mentioning new ideas or thoughts that you might think is necessary to include in your essay. It sounds confusing to say new things not mentioned in the essay, and it would be even more so if you don't elaborate on it either. Secondly, including transitions like "In summary", "In conclusion", and "In closing" sounds redundant and unnecessary or superfluous as well as boring and standard (this statement is only in my opinion, you can do whatever you want). This is because it's commonly used in a lot of essays and will make your essay seem basic, it also is not needed to write an effective conclusion paragraph, instead you can just start off with a strong concise sentence that's related to what you're asking.
I hoped this helped and you finish writing a good conclusion for your essay effectively. Happy Holidays!!