Just as an addition to the given answer.
There are basically two reasons as to why scholars declared the hadith from Sunan abi Dawod as da'if: (I've add a transliteration/translation of the full narrator chain)
حَدَّثَنَا مُحَمَّدُ بْنُ عَبَادَةَ الْوَاسِطِيُّ، حَدَّثَنَا يَزِيدُ بْنُ هَارُونَ، أَخْبَرَنَا إِسْمَاعِيلُ بْنُ عَيَّاشٍ، عَنْ ثَعْلَبَةَ بْنِ مُسْلِمٍ، عَنْ أَبِي عِمْرَانَ الأَنْصَارِيِّ، عَنْ أُمِّ الدَّرْدَاءِ، عَنْ أَبِي الدَّرْدَاءِ، قَالَ
We narrated from Muhammad ibn 'Abadah al-Wasiti who narrated it from Yazid ibn Harun who was informed by Ismai'l ibn 'Ayyach from Tha'alabah ibn Muslim from abu 'Imran al-Ansari from Umm al-Darda' Narrated Abu al-Darda:
قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِنَّ اللَّهَ أَنْزَلَ الدَّاءَ وَالدَّوَاءَ وَجَعَلَ لِكُلِّ دَاءٍ دَوَاءً فَتَدَاوَوْا وَلاَ تَدَاوَوْا بِحَرَامٍ " .
The Prophet (ﷺ) said: Allah has sent down both the disease and the cure, and He has appointed a cure for every disease, so treat yourselves medically, but use nothing unlawful. (Sunan abi Dawod or here)
The first is the addition "but use nothing unlawful" which doesn't appear in the most reliable hadith collections (the two sahihs) and most other hadith sources.
And the narrator Ismai'l ibn Ayyach who is a a-Shaam narrator and he is known for some weaknesses especially in his narrations from Hijaazi teachers. Al-Mundhiri and al-Manaawi (see for example here in Fayd al-Qadir فيض القدير ) and other early scholars said he is discussed (meaning that he might be upright, but not in all his narrations). al-Shawakani says in this case he is narrating from a Shaami teacher and wondered why others considered it as weak (see here in Arabic in Nail al-Awtaar نيل الأوطار ). Al-Albani however say that the issue is rather his teacher Tha'alabah ibn Muslim.
Al-Albani commented this hadith as follows (foot note) in his التعليقات الرضية على الروضة الندية Vol3 page 154:
الحديث صحيح – من حيث معناه – لشواهده
The hadith is sane (sahih) in meaning due to the witnessing narrations
This means there are many narrations that actually support the meaning for example using alcohol as a remedy is something declared as prohibited in this sahih hadith.